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THE  GILBERT  V.  HAMILTON 

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GIFT  OF  MARY  S.  HAMILTON 


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BIOLOGY 
AND    ITS    MAKERS 


With  Portraits  and  Other  Illustrations 


\    BY 

WILLIAM  A.  lLOCY,  Ph.D.,  Sc.D, 

Prqfeisor  in   Northivestern    Uni-versity 


THIRD  EDITION,  REVISED 


L^.  i 


NEW  YORK 

HENRY   HOLT   AND   COMPANY 

1915 


Copyright,  1908, 

BY 

HENRY  HOLT  AND  COMPANY 


Published  June,  1908 


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•  •    •    .  •  "   •      " 


,•     ~ 


To 

MY  GRADUATE  STUDENTS 

Who  have  worked  by  my  side  in  the  Laboratory 

Inspired  by  the  belief  that  those  who  seek  shall  find 

This  account  of  the  findings  of  some  of 

The  great  men  of  biological  science 

Is  dedicated  by 

The  Author 


C)du^'> 


PREFACE 


The  writer  is  annually  in  receipt  of  letters  from  students, 
teachers,  ministers,  medical  men,  and  others,  asking  for  in- 
formation on  topics  in  general  biology,  and  for  references  to 
the  best  reading  on  that  subject.  The  increasing  frequency 
of  such  inquiries,  and  the  wide  range  of  topics  covered,  have 
created  the  impression  that  an  untechnical  account  of  the 
rise  and  progress  of  biology  would  be  of  interest  to  a  con- 
siderable audience.  As  might  be  surmised,  the  references 
most  commonly  asked  for  are  those  relating  to  different 
phases  of  the  Evolution  Theory;  but  the  fact  is  usually  over- 
looked by  the  inquirers  that  some  knowledge  of  other  features 
of  biological  research  is  essential  even  to  an  intelligent  com- 
prehension of  that  theory. 

In  this  sketch  I  have  attempted  to  bring  under  one  view 
the  broad  features  of  biological  progress,  and  to  increase  the 
human  interest  by  writing  the  story  around  the  lives  of  the 
great  Leaders.  The  practical  execution  of  the  task  resolved 
itself  largely  into  the  question  of  what  to  omit.  The  number 
of  detailed  researches  upon  which  progress  in  biology  rests 
made  rigid  selection  necessary,  and  the  difficulties  of  separat- 
ing the  essential  from  the  less  important,  and  of  distinguish- 
ing between  men  of  temporary  notoriety  and  those  of  endur- 
ing fame,  have  given  rise  to  no  small  perplexities. 

The  aim  hks  been  kept  in  mind  to  give  a  picture  suffi- 
ciently diagrammatic  not  to  confuse  the  general  reader,  and 
it  is  hoped  that  the  omissions  which  have  seemed  necessar)^ 
will,  in  a  measure,  be  compensated  for  by  the  clearness  of 
the  picture.     References  to  selected  books  and  articles  have 


VI  PREFACE 

been  given  at  the  close  of  the  volume,  that  will  enable  readers 
who  wish  fuller  information  to  go  to  the  best  sources. 

The  book  is  divided  into  two  sections.  In  the  first  are 
considered  the  sources  of  the  ideas — except  those  of  organic 
evolution — that  dominate  biology,  and  the  steps  by  which 
they  have  been  molded  into  a  unified  science.  The  Doc- 
trine of  Organic  Evolution,  on  account  of  its  importance, 
is  reserved  for  special  consideration  in  the  second  section. 
This  is,  of  course,  merely  a  division  of  convenience,  since 
after  its  acceptance  the  doctrine  of  evolution  has  entered 
into  all  phases  of  biological  progress. 

The  portraits  with  which  the  text  is  illustrated  embrace 
those  of  nearly  all  the  founders  of  biology.  Some  of  the 
rarer  ones  are  unfamiliar  even  to  biologists,  and  have  been 
discovered  only  after  long  search  in  the  libraries  of  Europe 
and  America. 

An  orderly  account  of  the  rise  of  biology  can  hardly  fail 
to  be  of  service  to  the  class  of  inquirers  mentioned  in  the 
opening  paragraph.  It  is  hoped  that  this  sketch  will  also 
meet  some  of  the  needs  of  the  increasing  body  of  students 
who  are  doing  practical  work  in  biological  laboratories.  It  is 
important  that  such  students,  in  addition  to  the  usual  class- 
room instruction,  should  get  a  perspective  view  of  the  way 
in  which  biological  science  has  come  into  its  present  form. 

The  chief  purpose  of  the  book  will  have  been  met  if  I 
have  succeeded  in  indicating  the  sources  of  biological  ideas 
and  the  main  currents  along  which  they  have  advanced,  and 
if  I  have  succeeded,  furthermore,  in  making  readers  ac- 
quainted with  those  men  of  noble  purpose  whose  work  has 
created  the  epochs  of  biological  history,  and  in  showing  that 
there  has  been  continuity  of  development  in  biological 
thought. 

Of  biologists  who  may  examine  this  work  with  a  critical 
purpose,  I  beg  that  they  will  think  of  it  merely  as  an  outline 


PREFACE  vu 

sketch  which  does  not  pretend  to  give  a  complete  history  of 
biological  thought.  The  story  has  been  developed  almost 
entirely  from  the  side  of  animal  life;  not  that  the  botanical 
side  has  been  underestimated,  but  that  the  story  can  be  told 
from  either  side,  and  my  first-hand  acquaintance  with  botan- 
ical investigation  is  not  sufhcient  to  justify  an  attempt  to  es- 
timate its  particular  achievements. 

The  writer  is  keenly  aware  of  the  many  imperfections  in 
the  book.  It  is  inevitable  that  biologists  with  interests  in 
special  fields  will  miss  familiar  names  and  the  mention  of 
special  pieces  of  notable  work,  but  I  am  drawn  to  think  that 
such  omissions  will  be  viewed  leniently,  by  the  consideration 
that  those  best  able  to  judge  the  shortcomings  of  this  sketch 
will  also  best  understand  the  difficulties  involved. 

The  author  wishes  to  acknowledge  his  indebtedness  to 
several  publishing  houses  and  to  individuals  for  permission 
to  copy  cuts  and  for  assistance  in  obtaining  portraits.  He 
takes  this  opportunity  to  express  his  best  thanks  for  these 
courtesies.  The  parties  referred  to  are  the  director  of  the 
American  Museum  of  Natural  History;  D.  Appleton  &  Co.; 
P.  Blakiston's  Sons  &  Co.;  The  Macmillan  Company; 
The  Open  Court  Publishing  Company;  the  editor  of  the 
Popular  Science  Monthly \  Charles  Scribner's  Sons;  Pro- 
fessors Bateson,  of  Cambridge,  England;  Conklin,  of  Phila- 
delphia; Joubin,  of  Rennes,  France;  Nierstrasz,  of  Utrecht, 
Holland ;  Newcombe,  of  Ann  Arbor,  Michigan ;  Wheeler  and 
E.  B.  Wilson,  of  New  York  City.  The  editor  of  the  Popu- 
lar Science  Monthly  has  also  given  permission  to  reprint  the 
substance  of  Chapters  IV  and  X,  which  originally  ap- 
peared in  that  publication. 

W.  A.  L. 

Northwestern  University, 
Evanston,  III.,  April,  1908. 


PREFACE  TO  THE  THIRD  REVISED 
EDITION 


It  is  a  feature  of  scientific  knowledge  to  be  always  improv- 
ing, and,  owing  to  advances  since  the  publication  of  the 
earlier  editions,  many  of  the  matters  dealt  with  in  this  book 
appear  in  a  new  and  clearer  light.  But  since  the  book  aims 
primarily  to  point  out  the  epochs  of  advancement  as  well  as 
to  depict  the  conditions  under  which,  and  the  spirit  in  which 
advances  have  been  consummated,  the  subject  matter  of  the 
text  does  not  quickly  become  obsolete. 

While  retaining  substantially  its  original  form,  some  altera- 
tions have  been  made:  several  pages  have  been  rewritten  to 
convey  more  clearly  the  meaning,  as  in  reference  to  Mendel's 
discovery,  and  some  additions  have  been  introduced,  as  com- 
ments on  isolation  and  orthogenesis  as  factors  of  organic 
evolution.  The  important  contributions  of  Fritz  Schaudinn 
have  been  noted  and  the  discussion  of  the  antiquity  of  man 
has  been  considerably  extended.  Several  new  portraits  have 
been  substituted  for  those  of  the  earlier  editions  and  the  por- 
trait of  Schaudinn  has  been  added. 

W.  A.  L. 

March,  1915. 


CONTENTS 


PART   I 

The  Sources  of  Biological  Ideas  Except  Those  of 
Organic  Evolution 

CHAPTER  I 

PAGE 

An  Outline  of  the  Rise  of  Biology  and  of  the  Epochs  in  its 

History, 3 

Notable  advances  in  natural  science  during  the  nineteenth  century,  3. 
Biology  the  central  subject  in  the  history  of  opinion  regarding 
life,  4.  It  is  of  commanding  importance  in  the  world  of  science, 
5.  Difficulties  in  making  its  progress  clear,  5.  Notwithstanding 
its  numerous  details,  there  has  been  a  relatively  simple  and 
orderly  progress  in  biology,  6.  Many  books  about  the  facts  of 
biology,  many  excellent  laboratory  manuals,  but  scarcely  any 
attempt  to  trace  the  growth  of  biological  ideas,  6.  The  growth 
of  knowledge  regarding  organic  nature  a  long  story  full  of  human 
interest,  7.  The  men  of  science,  7.  The  story  of  their  aspira- 
tions and  struggles  an  inspiring  history,  8.  The  conditions  under 
which  science  developed,  8.  The  ancient  Greeks  studied  nature 
by  observation  and  experiment,  but  this  method  underwent 
eclipse,  9.  Aristotle  the  founder  of  natural  history,  9.  Science 
before  his  day,  9,  10.  Aristotle's  position  in  the  development  of 
science,  11.  His  extensive  knowledge  of  animals,  12.  His  scien- 
tific writings,  13.  Personal  appearance,  13.  His  influence,  15. 
Pliny:  his  writings  mark  a  decline  in  scientific  method,  16.  The 
arrest  of  inquiry  and  its  effects,  17.  A  complete  change  in  the 
mental  interests  of  mankind,  17.  Men  cease  to  observe  and  in- 
dulge in  metaphysical  speculation,  18.  Authority  declared  the 
source  of  knowledge,  18.  The  revolt  of  the  intellect  against  these 
conditions,  19.  The  renewal  of  observation,  19,  The  beneficent 
results  of  this  movement,  20.  Enumeration  of  the  chief  epochs 
in  biological  history:  renewal  of  observation,  20;  the  overthrow 
of  authority  in  science,  20.     Harvey  and  experimental  investiga- 


CONTENTS 

PAGE 

tion,  20;  introduction  of  microscopes,  20;  Linnaeus,  20;  Cuvier, 
20;  Bichat,  21;  Von  Baer,  21;  the  rise  of  physiology,  21;  the 
beginnings  of  evolutionary  thought,  21;  the  cell-theory,  21;  the 
discovery  of  protoplasm,  21. 


CHAPTER  II 

Vesalius  and  the  Overthrow  of  Authority  in  Science,    .       .    22 

Vesalius,  in  a  broad  sense,  one  of  the  founders  of  biology,  22.  A  pic- 
ture of  the  condition  of  anatomy  before  he  took  it  up,  23.  Galen: 
his  great  influence  as  a  scientific  writer,  24.  Anatomy  in  the 
Middle  Ages,  24.  Predecessors  of  Vesalius:  Mundinus,  Beran- 
garius,  Sylvius,  26.  Vesalius  gifted  and  forceful,  27.  His  im- 
petuous nature,  28.  His  reform  in  the  teaching  of  anatomy,  28. 
His  physiognomy,  30.  His  great  book  (1543),  32.  A  descrip- 
tion of  its  illustrations,  32,  ^;^.  Curious  conceits  of  the  artist,  34. 
Opposition  to  Vesalius:  curved  thigh  bones  due  to  wearing  tight 
trousers,  the  resurrection  bone,  34,  35.  The  court  physician,  36. 
Close  of  his  life,  36.  Some  of  his  successors:  Eustachius  and 
Fallopius,  37.  The  especial  service  of  Vesalius:  he  overthrew 
dependence  on  authority  and  reestablished  the  scientific  method 
of  ascertaining  truth,  38. 

CHAPTER  III 

William  Harvey  and  Experimental  Observation,      .        .        .39 

Harvey's  work  complemental  to  that  of  Vesalius,  39.  Their  com- 
bined labors  laid  the  foundations  of  the  modern  method  of  in- 
vestigating nature,  39.  Harvey  introduces  experiments  on  living 
organisms,  40.  Harvey's  education,  40.  At  Padua,  comes 
under  the  influence  of  Fabricius,  41.  Return  to  England,  42. 
His  personal  quahties,  42-45.  Harvey's  writings,  45.  His  great 
classic  on  movement  of  the  heart  and  blood  (1628),  46.  His 
demonstration  of  circulation  of  the  blood  based  on  cogent  rea- 
soning; he  did  not  have  ocular  proof  of  its  passage  through 
capillaries,  47.  Views  of  his  predecessors  on  the  movement  of 
the  blood,  48.  Servetus,  50.  Realdus  Columbus,  50.  Caesal- 
pinus,  51.  The  originality  of  Harvey's  views,  51.  Harvey's 
argument,  51.  Harvey's  influence,  52.  A  versatile  student; 
work  in  other  directions,  52.  His  discovery  of  the  circulation 
created  modern  physiology,  52.  His  method  of  inquiry  became 
a  permanent  part  of  biological  science,  53. 


CONTENTS  XI 

PAGE 

CHAPTER  IV 

The  Introduction  of  the  Microscope  and  the  Progress  of  Inde- 
pendent Observation, 54 

The  pioneer  microscopists:  Hooke  and  Grew  in  England;  Malpighi 
in  Italy  and  Swammerdam  and  Leeuwenhoek  in  Holland,  54. 
Robert  Hooke,  5  5 .  His  microscope  and  the  micrographia  ( 1 665 ) , 
56.  Grew  one  of  the  founders  of  vegetable  histology,  56.  Mal- 
pighi, 1 628-1 694,  58.  Personal  qualities,  58.  Education,  60. 
University  positions,  60,  61.  Honors  at  home  and  abroad,  61. 
Activity  in  research,  62.  His  principal  writings:  Monograph 
on  the  silkworm,  63;  anatomy  of  plants,  66;  work  in  embry- 
ology, 66.  Jan  Swammerdam,  1 637-16S0,  67.  His  temperament, 
67.  Early  interest  in  natural  history,  68.  Studies  medicine,  68. 
Important  observations,  68.  Devotes  himself  to  minute  anat- 
omy, 70.  Method  of  working,  71.  Great  intensity,  70.  High 
quality  of  his  work,  72.  The  Biblia  Natura,  73.  Its  publica- 
tion delayed  until  fifty-seven  years  after  his  death,  73.  Illustra- 
tions of  his  anatomical  work,  74-76.  Antony  van  Leeuwenhoek, 
1632-1723,77.  A  composed  and  better-balanced  man,  77.  Self- 
taught  in  science,  the  effect  of  this  showing  in  the  desultory  char- 
acter of  his  observations,  77,  87.  Physiognomy,  78.  New  bio- 
graphical facts,  78.  His  love  of  microscopic  observation,  80. 
His  microscopes,  81.  His  scientific  letters,  83.  Observes  the 
capillary  circulation  in  1686,  84.  His  other  discoveries,  86. 
Comparison  of  the  three  men:  the  two  university -trained  men 
left  coherent  pieces  of  work,  that  of  Leeuwenhoek  was  discursive, 
87,  The  combined  force  of  their  labors  marks  an  epoch,  88. 
*  The  new  intellectual  movement  now  well  under  way,  88, 


CHAPTER  V 

The  Progress  of  Minute  Anatomy, 89 

Progress  in  minute  anatomy  a  feature  of  the  eighteenth  century. 
Attractiveness  of  insect  anatomy.  Enthusiasm  awakened  by  the 
delicacy  and  perfection  of  minute  structure,  89.  Lyonet,  1707- 
1789,  90.  Description  of  his  remarkable  monograph  on  the 
anatomy  of  the  willow  caterpillar,  91.  Selected  illustrations, 
92-94.  Great  detail — 4,041  muscles,  91.  Extraordinary  character 
of  his  drawings,  90.  A  model  of  detailed  dissection,  but  lacking 
in  comparison  and  insight,  92.     The  work  of  Reaumur,  Roesel, 


XU  CONTENTS 

PAGE 

and  De  Geer  on  a  higher  plane  as  regards  knowledge  of  insect  life, 
95.  Straus-Diirckheim's  monograph  on  insect  anatomy,  96.  Rivals 
that  of  Lyonet  in  detail  and  in  the  execution  of  the  plates,  99. 
His  general  considerations  now  antiquated,  99.  He  attempted 
to  make  insect  anatomy  comparative,  100.  Dufour  endeavors  to 
found  a  broad  science  of  insect  anatomy,  100.  Newport,  a  very 
skilful  dissector,  with  philosophical  cast  of  mind,  who  recognizes 
the  value  of  embryology  in  anatomical  work,  100.  Leydig  starts 
a  new  kind  of  insect  anatomy  embracing  microscopic  structure 
(histology),  102.  This  the  beginning  of  modern  work,  102. 
Structural  studies  on  other  small  animals,  103.  The  discovery 
of  the  simplest  animals,  104.  Observations  on  the  microscopic 
animalcula,  105.  The  protozoa  discovered  in  1675  by  Leeuwen 
hoek,  105.  Work  of  O.  F.  Miiller,  1786,  106.  Of  Ehrenberg 
1838,  107.    Recent  observations  on  protozoa,  109. 


CHAPTER  VI 

LiNN^us  AND  Scientific  Natural  History, 

Natural  history  had  a  parallel  development  with  comparative  anatomy, 
no.  The  Physiologus,  or  sacred  natural  history  of  the  Middle 
Ages,  no,  III.  The  lowest  level  reached  by  zoology,  in.  The 
return  to  the  science  of  Aristotle  a  real  advance  over  the  Physiol- 
ogus, 112.  The  advance  due  to  Wotton  in  1552,  112.  Gesner, 
1516-1565.  High  quahty  of  his  Historia  Animalium,  112-114. 
The  scientific  writings  of  Jonson  and  Aldrovandi,  114.  John 
Ray  the  forerunner  of  Linnjeus,  115.  His  writings,  117.  Ray's 
idea  of  species,  117.  Linnaeus  or  Linne,  118.  A  unique  ser- 
vice to  natural  history.  Brings  the  binomial  nomenclature  into 
general  use,  118.  Personal  history,  119.  Quality  of  his  mind, 
120.  His  early  struggles  with  poverty,  120.  Gets  his  degree  in 
Holland,  121.  Publication  of  the  6'>'5tewa  iVa/wr«  in  1735,  121. 
Return  to  Sweden,  123.  Success  as  a  university  professor  in  Up- 
sala,  123.  Personal  appearance,  125.  His  influence  on  natural 
history,  125,  His  especial  service,  126.  His  idea  of  species, 
128.  Summary,  129.  Reform  of  the  Linnaean  system,  130- 
138.  The  necessity  of  reform,  130.  The  scale  of  being,  131. 
Lamarck  the  first  to  use  a  genealogical  tree,  132.  Cuvier's 
four  blanches,  132.  Alterations  by  Von  Siebold  and  Leuckart, 
134-137.  Tabularviewof  classifications,  138.  General  biologi- 
cal progress  from  Linnaeus  to  Darwin.  Although  details  were 
multiplied,  progress  was  by  a  series  of   steps,   138.     Analysis 


CONTENTS  xm 

PAGE 

of  animals  proceeded  from  the  organism  to  organs,  from  organs 
to  tissues,  from  tissues  to  cells,  the  elementary  parts,  and  finally 
to  protoplasm,  13Q-140.  The  physiological  side  had  a  par- 
allel development,  140. 


CHAPTER  VII 

CUVIER  AND  THE  RiSE  OF  COMPARATIVE  AnATOMY,      .  .  .  .    I4I 

The  study  of  internal  structure  of  living  beings,  at  first  merely  de- 
scriptive, becomes  comparative,  141.  Belon,  141.  Severinus 
writes  the  first  book  devoted  to  comparative  anatomy  in  1645, 
143.  The  anatomical  studies  of  Camper,  143.  John  Hunter, 
144..  Personal  characteristics,  145.  His  contribution  to  prog- 
ress, 146.  Vicq  d'Azyr  the  greatest  comparative  anatomist 
before  Cuvier,  146-148.  Cuvier  makes  a  comprehensive  study 
of  the  structure  of  animals,  148.  His  birth  and  early  education, 
149.  Life  at  the  sea  shore,  150.  Six  years  of  quiet  study  and 
contemplation  lays  the  foundation  of  his  scientific  career,  150. 
Goes  to  Paris,  151.  His  physiognomy,  152.  Comprehensiveness 
of  his  mind,  154.  Founder  of  comparative  anatomy,  155.  His 
domestic  life,  155.  Some  shortcomings,  156.  His  break  with 
early  friends,  156.  Estimate  of  George  Bancroft,  156.  Cuvier's 
successors:  Milne-Edwards,  157;  Lacaze-Duthiers,  157;  Rich- 
ard Owen,  158;  Oken,  160;  J.  Fr.  Meckel,  162;  Rathke,  163; 
J.  Miiller,  163;  Karl  Gegenbaur,  164;  E.  D.  Cope,  165.  Com- 
parative anatomy  a  rich  subject,  165.  It  is  now  becoming  exper- 
imental, 165. 


CHAPTER  VIII 

Bichat  and  the  Birth  of  Histology, 166 

Bichat  one  of  the  foremost  men  in  biological  history.  He  carried  the 
analysis  of  animal  organization  to  a  deeper  level  than  Cuvier,  166. 
Buckle's  estimate,  166.  Bichat  goes  to  Paris,  167.  Attracts  at- 
tention in  Desault's  classes,  167.  Goes  to  live  with  Desault,  168. 
His  fidelity  and  phenomenal  industry,  168.  Personal  appear- 
ance, 168.  Begins  to  publish  researches  on  tissues  at  the  age  of 
thirty,  170.  His  untimely  death  at  thirty-one,  170.  Influence 
of  his  vmtings,  170.  His  more  notable  successors:  Schwann, 
171;  Koelliker,  a  striking  figure  in  the  development  of  biology, 
171;  Max  Schultze,  172;  Rudolph  Virchow,  174;  Leydig,  175; 
Ramon  y  Cajal,  176.     Modern  text-books  on  histology,  177. 


Sav  CONTENTS 


CHAPTER  IX 

Thi  Rise  of  Physiology — Harvey.    Haller.    Johannes  Muller,  179 

Physiology  had  a  parallel  development  with  anatomy,  179.  Physiol- 
ogy of  the  ancients,  179.  Galen,  180.  Period  of  Harvey,  180. 
His  demonstration  of  circulation  of  the  blood,  180.  His  method 
of  experimental  investigation,  181.  Period  of  Haller,  181.  Phys- 
iology developed  as  an  independent  science,  183.  Haller's  per- 
sonal characteristics,  181.  His  idea  of  vital  force,  182.  His  book 
on  the  Elements  of  Physiology  a  valuable  work,  183.  Discovery 
of  oxygen  by  Priestley  in  1774,  183.  Charles  Bell's  great  discov- 
ery on  the  nervous  system,  183.  Period  of  Johannes  Muller,  184. 
A  man  of  unusual  gifts  and  personal  attractiveness,  185.  His 
personal  appearance,  185.  His  great  influence  over  students,  185. 
His  especial  service  was  to  make  physiology  broadly  comparative, 
186.  His  monumental  Handbook  of  Physiology,  186.  Unex- 
ampled accuracy  in  observation,  186.  Introduces  the  principles 
of  psychology  into  physiology,  186.  Physiology  after  Muller, 
188-195.  Ludwig,  188.  Du  Bois-Reymond,  189.  Claude 
Bernard,  190.  Two  directions  of  growth  in  physiology — the 
chemical  and  the  physical,  192.  Influence  upon  biology,  193. 
Other  great  names  in  physiology,  194. 


CHAPTER  X 

Von  Baer  and  the  Rise  of  Embryology, 195 

Romantic  nature  of  embryology,  195.  Its  importance,  195.  Rudi- 
mentary organs  and  their  meaning,  195.  The  domain  of  em- 
bryology, 196.  Five  historical  periods,  196.  The  period  of 
Harvey  and  Malpighi,  197-205.  The  embryological  work  of 
these  two  men  insufficiently  recognized,  197.  Harvey's  pioneer 
attempt  critically  to  analyze  the  process  of  development,  198.  His 
teaching  regarding  the  nature  of  development,  199.  His  treatise 
on  Generation,  199.  The  frontispiece  of  the  edition  of  165 1,  201, 
202.  Malpighi's  papers  on  the  formation  of  the  chick  within  the 
egg,  202.  Quality  of  his  pictures,  202.  His  belief  in  preformation, 
207.  Malpighi's  rank  as  embryologist,  205.  The  period  of 
Wolff,  205-214.  Rise  of  the  theory  of  predelineation,  206. 
Sources  of  the  idea  that  the  embryo  is  preformed  within  the  egg, 
207.  Malpighi's  observations  quoted,  207.  Swammerdam's 
view,  208.     Leeuwenhoek  and  the  discovery  of  the  sperm,  208. 


CONTENTS  XV 

PAGE 

Bonnet's  views  on  emhoUement,  208.  Wolff  opposes  the  doctrine 
of  preformation,  210.  His  famous  Theory  of  Generation  (1759), 
210.  Sketches  from  this  treatise,  209.  His  views  on  the  directing 
force  in  development,  211.  His  highest  grade  of  work,  211. 
Opposition  of  Haller  and  Bonnet,  211.  Restoration  of  Wolff's 
views  by  Meckel,  212.  Personal  characteristics  of  Wolff,  213. 
The  period  of  Von  Baer,  214-222.  The  greatest  personality  in 
embryology,  215.  His  monumental  work  on  the  Development  of 
Animals  a  choice  combination  of  observation  and  reflection,  215. 
Von  Baer's  especial  service,  217.  Establishes  the  germ -layer 
theory,  218.  Consequences,  219.  His  influence  on  embryology, 
220.  The  period  from  Von  Baer  to  Balfour,  222-226.  The  proc- 
ess of  development  brought  into  a  new  light  by  the  cell-theory, 
222.  Rathke,  Remak,  Koelliker,  Huxley,  Kowalevsky,  223,  224. 
Beginnings  of  the  idea  of  germinal  continuity,  225.  Influence  of 
the  doctrine  of  organic  evolution,  226.  The  period  of  Balfour, 
with  an  indication  of  present  tendencies,  226-236.  The  great 
influence  of  Balfour's  Comparative  Embryology,  226.  Person- 
ality of  Balfour,  228.  His  tragic  fate,  228.  Interpretation  of  the 
embryological  record,  229.  The  recapitulation  theory,  230. 
Oskar  Hertwig,  232.  Wilhelm  His,  232.  Recent  tendencies; 
Experimental  embryology,  232;  Cell-lineage,  234;  Theoretical 
discussions,  235. 

CHAPTER  XI 

The  Cell-Theory — Schleiden.     Schwann.     Schultze,  .        .237 

Unifying  power  of  the  cell-theory,  237.  Vague  foreshadowings,  237. 
The  first  pictures  of  cells  from  Robert  Hooke's  Micrographia,  238. 
Cells  as  depicted  by  Malpighi,  Grew,  and  Leeuwenhoek,  239,  240. 
Wolff  on  cellular  structure,  240,  241.  Oken,  241.  The  an- 
nouncement of  the  cell-theory  in  1838-39,  242.  Schleiden  and 
Schwann  co-founders,  243.  Schleiden's  work,  243.  His  ac- 
quaintance with  Schwann,  243.  Schwann's  personal  appearance, 
244.  Influenced  by  Johannes  Miiller,  245.  The  cell-theory  his 
most  important  work,  246.  Schleiden,  his  temperament  and  dis- 
position, 247.  Schleiden's  contribution  to  the  cell-theory,  247. 
Errors  in  his  observations  and  conclusions,  248.  Schwann's 
treatise,  248.  Purpose  of  his  researches,  249.  Quotations  from 
his  microscopical  researches,  249.  Schwann's  part  in  establish- 
ing the  cell-theory  more  important  than  that  of  Schleiden,  250. 
Modification  of  the  cell-theory,  250.  Necessity  of  modifications, 
250.     The  discovery  of  protoplasm,  and  its  effect  on  the  cell- 


XVI  CONTENTS 

PAGE 

theory,  250.  The  cell-theory  becomes  harmonized  yviih  the  pro- 
toplasm doctrine  of  Max  Schultze,  251.  Further  modifications  of 
the  cell-theory,  252.  Origin  of  cells  in  tissues,  252.  Structure  of 
the  nucleus,  253.  Chromosomes,  254.  Centrosome,  256.  The 
principles  of  heredity  as  related  to  cellular  studies,  257.  Ver- 
worn's  definition,  258.  Vast  importance  of  the  cell-theory  in 
advancing  biology,  258. 


CHAPTER    XII 

Protoplasm  the  Physical  Basis  of  Life, 259 

Great  influence  of  the  protoplasm  doctrine  on  biological  progress,  259. 
Protoplasm,  259.  Its  properties  as  discovered  by  examination  of 
the  amoeba,  260.  Microscopic  examination  of  a  transparent  leaf, 
261.  Unceasing  activity  of  its  protoplasm,  261.  The  wonderful 
energies  of  protoplasm,  261.  Quotation  from  Huxley,  262.  The 
discovery  of  protoplasm  and  the  essential  steps  in  recognizing 
the  part  it  plays  in  Hving  beings,  262-275.  Dujardin,  262.  His 
personality,  263.  Education,  263.  His  contributions  to  science, 
264.  His  discovery  of  "  sarcode  V  in  the  simplest  animals,  in  1835, 
266.  Purkinje,  in  1840,  uses  the  term  protoplasma,  267.  Von 
Mohl,  in  1846,  brings  the  designation  protoplasm  into  general 
use,  268.  Cohn,  in  1850,  maintains  the  identity  of  sarcode  and 
protoplasm,  270.  Work  of  De  Bary  and  Virchow,  272.  Max 
Schultze,  in  1861,  shows  that  there  is  a  broad  likeness  between 
the  protoplasm  of  animals  and  plants,  and  establishes  the  proto- 
plasm doctrine.  The  university  life  of  Schultze.  His  love  of 
music  and  science.  Founds  a  famous  biological  periodical,  272- 
274.  The  period  from  1840  to  i860  an  important  one  for  biol- 
ogy, 274. 

CHAPTER  XIII 

The  Work  of  Pasteur,  Koch,  and  Others, 276 

The  bacteria  discovered  by  Leeuwenhoek  in  1687,  276.  The  develop- 
ment of  the  science  of  bacteriology  of  great  importance  to  the 
human  race,  276.  Some  general  topics  connected  with  the  study 
of  bacteria,  277.  The  spontaneous  origin  of  life,  277-293.  Bio- 
genesis or  abiogenesis,  277.  Historical  development  of  the  ques- 
tion, 277.  I.  From  Aristotle,  325  B.C.,  to  Redi,  1668,  278.  The 
spontaneous  origin  of  living  forms  universally  believed  in,  278. 
Illustrations,  278.    II.  From  Redi  to  Schwann,  278-284.    Redi, 


CONTENTS  XVU 

PAGB 

in  1668,  puts  the  question  to  experimental  test  and  overthrows 
the  belief  in  the  spontaneous  origin  of  forms  visible  to  the  un- 
aided eye,  279.  The  problem  narrowed  to  the  origin  of  micro- 
scopic animal  cula,  281.  Needham  and  Buff  on  test  the  ques- 
tion by  the  use  of  tightly  corked  vials  containing  boiled  or- 
ganic solutions,  281.  Microscopic  life  appears  in  their  infusions, 
282.  Spallanzani,  in  1775,  uses  hermetically  sealed  glass  flasks 
and  gets  opposite  results,  282.  The  discovery  of  oxygen  raises 
another  question :  Does  prolonged  heat  change  its  vitalizing  prop- 
erties? 284.  Experiments  of  Schwann  and  Schulze,  1836-37, 
284.  The  question  of  the  spontaneous  origin  of  microscopic  life 
regarded  as  disproved,  286.  III.  Pouchet  reopens  the  question 
in  1858,  maintaining  that  he  finds  microscopic  life  produced  in 
sterilized  and  hermetically  sealed  solutions,  286.  The  question 
put  to  rest  by  the  brilliant  researches  of  Pasteur  and  of  Tyndall, 
288,  289.  Description  of  Tyndall's  apparatus  and  his  use  of  op- 
tically pure  air,  290.  Weismann's  theoretical  speculations  re- 
garding the  origin  of  biophors,  292.  The  germ -theory  of  disease, 
293-304.  The  idea  of  contagium  vivum  revived  in  1840,  293. 
Work  of  Bassi,  294.  Demonstration,  in  1877,  of  the  actual  con- 
nection between  anthrax  and  splenic  fever,  294.  Veneration  of 
Pasteur,  294.  His  personal  quaUties,  296.  Fihal  devotion,  297. 
Steps  in  his  intellectual  development,  298.  His  investigation  of 
diseases  of  wine  (1868),  299.  Of  the  silk-worm  plague  (1865-68), 
299.  His  studies  on  the  cause  and  prevention  of  disease  con- 
stitute his  chief  service  to  humanity,  299.  Establishment  of  the 
Pasteur  Institute  in  Paris,  299.  Recent  developments,  300. 
Robert  Koch;  his  services  in  discovering  many  bacteria  of  dis- 
ease, 300.  Sir  Joseph  Lister  and  antiseptic  surgery,  302.  Bac- 
teria in  their  relation  to  agriculture,  soil  inoculation,  etc.,  303. 
Knowledge  of  bacteria  as  related  to  the  growth  of  general  biol- 
ogy, 304. 

CHAPTER  XIV 

Heredity  and  Germinal  Continuity — Mendel.     Galton.    Weis- 

MANN, 306 

The  hereditary  substance  and  the  bearers  of  heredity,  306.  The 
nature  of  inheritance,  306,  Darwin's  theory  of  pangenesis,  307. 
The  theory  of  pangens  replaced  by  that  of  germinal  continuity, 
308.  Exposition  of  the  theory  of  germinal  continuity,  309.  The 
law  of  cell-succession,  309.  Omnis  cellula  e  cellula,  310.  The 
continuity  of  hereditary  substance,  310.     Early  writers,  311. 


xviii  CONTENTS 

PAGE 

Weismann,  312.  Germ-cells  and  body  cells,  312.  The  hered- 
itary substance  is  the  germ-plasm,  312.  It  embodies  all  the  past 
history  of  protoplasm,  312.  The  more  precise  investigation  of 
the  material  basis  of  inheritance,  312.  The  nucleus  of  '^ells,  312. 
The  chromosomes,  313,  The  fertilized  ovum,  the  starting-point 
of  new  organisms,  314.  Behavior  of  the  nucleus  during  division, 
314.  The  mixture  of  parental  qualities  in  the  chromosomes,  314. 
Prelocalized  areas  in  the  protoplasm  of  the  egg,  315.  The  in- 
heritance of  acquired  characteristics,  315.  The  application  of 
statistical  methods  and  experiments  to  the  study  of  heredity,  315. 
Mendel's  important  discovery  of  alternative  inheritance,  317. 
Francis  Galton,  319.  Karl  Pearson,  321,  Experiments  on  in- 
heritance, 321. 

CHAPTER  XV 

The  Science  of  Fossil  Remains,      .  322 

Extinct  forms  of  life,  322.  Strange  views  regarding  fossils,  322. 
Freaks  of  nature,  323.  Mystical  explanations,  323.  Large  bones 
supposed  to  be  those  of  giants,  3  24.  Determination  of  the  nature 
of  fossils  by  Steno,  324.  Fossil  deposits  ascribed  to  the  Flood, 
325.  Mosaic  deluge  regarded  as  of  universal  extent,  326,  The 
comparison  of  fossil  and  living  animals  of  great  importance,  327. 
Cuvier  the  founder  of  vertebrate  palaeontology.  327.  Lamarck 
founds  invertebrate  palaeontology,  328.  Lamarck's  conception  of 
the  meaning  of  fossils  more  scientific  than  Cuvier's,  329.  The 
arrangement  of  fossils  in  strata,  330.  William  Smith,  330.  Sum- 
mary of  the  growth  of  the  science  of  fossil  life,  330.  Fossil  re- 
mains as  an  index  to  the  past  history  of  the  earth,  332.  Epoch- 
making  work  of  Charles  Lyell,  332.  Effect  of  the  doctrine  of 
organic  evolution  on  palaeontology,  334.  Richard  Owen's 
studies  on  fossil  animals,  334,  Agassiz  and  the  parallelism  be- 
tween fossil  forms  of  life  and  stages  in  the  development  of 
animals,  336.  Huxley'sgeological  work,  337.  Leidy,  339.  Cope, 
339.  Marsh,  340.  Carl  Zittel's  writings  and  influence,  340. 
Henry  F.  Osborn,  341.  Method  of  collecting  fossils,  342,  Fossil 
remains  of  man,  342.  Discoveries  in  the  Fayiim  district  of 
Africa,  343. 


CONTENTS  xix 

PART  II 

The  Doctrine  of  Organic  Evolution 
CHAPTER  XVI 

PAGE 

What  Evolution  Is:  The  Evidence  upon  which  it  Rests,  etc.,  .  347 
Great  vagueness  regarding  the  meaning  of  evolution,  348.  Causes  for 
this,  348.  The  confusion  of  Darwinism  with  organic  evolution, 
349.  The  idea  that  the  doctrine  is  losing  ground,  349.  Scientific 
controversies  on  evolution  relate  to  the  factors,  not  to  the  fact,  of 
evolution,  349.  Nature  of  the  question:  not  metaphysical,  not 
theological,  but  historical,  350.  The  historical  method  applied 
to  the  study  of  animal  life,  351.  The  diversity  of  living  forms, 
351.  Are  species  fixed  in  nature?  352,  Wide  variation  among  an- 
imals, 352.  Evolutionary  series:  The  shells  of  Slavonia  and 
Steinheim,  353-355.  Evolution  of  the  horse,  356.  The  collec- 
tion of  fossil  horses  at  the  American  Museum  of  Natural  History, 
New  York,  357,  The  genealogy  of  the  horse  traced  for  more 
than  two  million  years,  356.  Connecting  forms:  the  archaeop- 
teryx  and  pterodactyls,  360.  The  embryolo^ical  record  and  its 
connection  with  evolution,  360.  Clues  to  the  past  history  of 
animals,  360.  Rudimentary  organs,  363-365.  Hereditary  sur- 
vivals in  the  human  body,  365.  Remains  of  the  scaffolding  for 
its  building,  366.  Antiquity  of  man,  366.  Pre-human  types,  367. 
Virtually  three  links:  the  Java  man;  the  Neanderthal  skull;  the 
early  neolithic  man  of  Engis,  366-370.  Evidences  of  man's  evo- 
lution based  on  palaeontology,  embryology,  and  archaeology,  372. 
Mental  evolution,  372.  Sweep  of  the  doctrine  of  organic  evolu- 
tion, 372-373. 

CHAPTER  XVII 

Theories  of  Evolution — Lamarck.    Darwin,        .        .  .        .374 

The  attempt  to  indicate  the  active  factors  of  evolution  is  the  source  of 
the  different  theories,  374.  The  theories  of  Lamarck,  Darwin, 
and  Weismann  have  attracted  the  widest  attention,  375.  La- 
marck, the  man,  374-380.  His  education,  376.  Leaves  priestly 
studies  for  the  army,  376.  Great  bravery,  377.  Physical  injury 
makes  it  necessary  for  him  to  give  up  military  life,  377.  Por- 
trait, 379.    Important  work  in  botany,  377.    Pathetic  poverty 


XX  CONTENTS 

PAGE 

and  neglect,  378.  Changes  from  botany  to  zoology  at  the  age  of 
fifty  years,  378.  Profound  influence  of  this  change  in  shaping 
his  ideas,  380.  His  theory  of  evolution,  380-386.  First  public 
announcement  in  1800,  381.  His  Philosophie  Zoologique  pub- 
lished in  1809,  381.  His  two  laws  of  evolution,  382.  The  first 
law  embodies  the  principle  of  use  and  disuse  of  organs,  the  second 
that  of  heredity,  380.  A  simple  exposition  of  his  theory,  383. 
His  employment  of  the  word  hesoin,  383.  Lamarck's  view  of 
heredity,  383.  His  belief  in  the  inheritance  of  acquired  char- 
acters, 383.  His  attempt  to  account  for  variation,  383.  Time 
and  favorable  conditions  the  two  principal  means  employed  by 
nature,  384.  Salient  points  in  Lamarck's  theory,  384.  His 
definition  of  species,  385.  Neo-Lamarckism,  386.  Darwin.  His 
theory  rests  on  three  sets  of  facts.  The  central  feature  of  his 
theory  is  natural  selection.  Variation,  386.  Inheritance,  388. 
Those  variations  v/ill  be  inherited  that  are  of  advantage  to  the 
race,  389.  Illustrations  of  the  meaning  of  natural  selection,  389- 
S95.  The  struggle  for  existence  and  its  consequences,  390.  Vari- 
ous aspects  of  natural  selection,  390.  It  does  not  always  operate 
toward  increasing  the  efficiency  of  an  organ — short-winged 
beetles,  391.  Color  of  animals,  392.  Mimicry,  393.  Sexual 
selection,  394.  Inadequacy  of  natural  selection,  395.  Darwin 
the  first  to  call  attention  to  the  inadequacy  of  this  principle,  395. 
Confusion  between  the  theories  of  Lamarck  and  Darwin,  396. 
Illustrations,  397.  The  Origin  of  Species  published  in  1859, 
397.    Other  writings  of  Darwin,  397. 


CHAPTER  XVIII 

Theories  Continued — Weismann.  De  Vries,  ....  398 
Weismann's  views  have  passed  through  various  stages  of  remodeling, 
398.  The  Evolution  Theory  published  in  1904  is  the  best  ex- 
position of  his  views,  398.  His  theory  the  field  for  much  contro- 
versy. Primarily  a  theory  of  heredity,  399.  Weismann's  theory 
summarized,  399.  Continuity  of  the  germ-plasm  the  central  idea 
in  Weismann's  theory,  400.  Complexity  of  the  germ-plasm.  Il- 
lustrations, 401.  The  origin  of  variations,  402.  The  union  of 
two  complex  germ-plasms  gives  rise  to  variations,  402.  His  ex- 
tension of  the  principle  of  natural  selection — germinal  selection, 
403.  The  inheritance  of  acquired  characters,  404.  Weismann's 
analysis  of  the  subject  the  best,  403.  Illustrations,  405.  The 
question  still  open  to  experimental  observation,  405.     Weis- 


CONTENTS  xxj 

PAGE 

mann's  personality,  406.  Quotation  from  his  autobiography,  408. 
The  mutation  theory  of  De  Vries,  408.  An  important  contribu- 
tion. His  appUcation  of  experiments  commendable,  40Q.  The 
mutation  theory  not  a  substitute  for  that  of  natural  selection,  410. 
Tendency  toward  a  reconciliation  of  apparently  conflicting  views, 
410.  Summary  of  the  salient  features  of  the  theories  of  Lamarck, 
of  Darwin,  of  Weismann,  and  De  Vries,  411.  Causes  for  bewil- 
derment in  the  popular  mind  regarding  the  different  forms  of  the 
evolution  theory,  414. 

CHAPTER  XIX 

The  Rise  of  Evolutionary  Thought, 415 

Opinion  before  Lamarck,  415.  Views  of  certain  Fathers  of  the 
Church,  416.  St.  Augustine,  416,  St.  Thomas  Aquinas,  417. 
The  rise  of  the  doctrine  of  special  creation,  418.  Suarez,  418. 
Effect  of  John  Milton's  writings,  417.  Forerunners  of  Lamarck: 
Buffon,  Erasmus  Darwin,  Goethe,  419.  Statement  of  Buffon's 
views  on  evolution,  420.  Erasmus  Darwin  the  greatest  of  La- 
marck's predecessors,  421.  His  writings,  422.  Paley's  Natural 
Theology  directed  against  them,  422,  Goethe's  connection  with 
evolutionary  thought,  422.  Causes  for  the  neglect  of  Lamarck's 
theoretical  writings,  422.  The  temporary  disappearance  of  the 
doctrine  of  organic  evolution.  423.  Cuvier's  opposition,  423. 
The  debate  between  Cuvier  and  St.  Hilaire,  423.  Its  effect,  425. 
Influence  of  Lyell's  Principles  of  Geology,  426.  Herbert  Spen- 
cer's analysis  in  1852,  427.  Darwin  and  Wallace,  428.  Circum- 
stances under  which  their  work  was  laid  before  the  Linnaean 
Society  of  London,  428.  The  letter  of  transmission  signed  by 
Lyell  and  Hooker,  428-430.  The  personality  of  Darwin,  430. 
Appearance,  431.  His  charm  of  manner,  431.  Affectionate 
consideration  at  home,  432.  Unexampled  industry  and  con- 
scientiousness in  the  face  of  ill  health,  432,  434.  His  early 
life  and  education,  ^^:^.  Voyage  of  the  Beagle,  433.  The  re- 
sults of  his  five  years'  voyage,  434.  Life  at  Down,  434. 
Parallelism  in  the  thought  of  Darwin  and  Wallace,  435.  Dar- 
win's account  of  how  he  arrived  at  the  conception  of  natural 
selection,  435.  Wallace's  narrative,  435.  The  Darwin-Wallace 
theory  launched  in  1858,  437.  Darwin's  book  on  The  Origin  of 
Species  regarded  by  him  as  merely  an  outline,  437.  The  spread 
of  the  doctrine  of  organic  evolution,  437.  Huxley  one  of  its  great 
popular  exponents,  438.  Haeckel,  439.  After  Darwin,  the  prob- 
lem was  to  explain  phenomena,  441. 


xxii  CONTENTS 


PAGE 

CHAPTER  XX 

Retrospect  and  Prospect.  Present  Tendencies  in  Biology,  .  442 
Biological  thought  shows  continuity  of  development,  442.  Character 
of  the  progress — a  crusade  against  superstition,  442.  The  first 
triumph  of  the  scientific  method  was  the  overthrow  of  authority, 
443.  The  three  stages  of  progress — descriptive,  comparative,  ex- 
perimental, 443.  The  notable  books  of  biology  and  their  authors, 
443-445.  Recent  tendencies  in  biology:  higher  standards,  445; 
improvement  in  the  tools  of  science,  446;  advance  in  methods, 
447;  experimental  work,  447;  the  growing  interest  in  the  study 
of  processes,  448;  experiments  applied  to  heredity  and  evolution, 
to  fertilization  of  the  egg,  and  to  animal  behavior,  448,  449. 
Some  tendencies  in  anatomical  studies,  450.  Cell-lineage,  450, 
New  work  on  the  nervous  system,  451,  The  application  of 
biological  facts  to  the  benefit  of  mankind,  451.  Technical  biol- 
ogy, 451.  Soil  inoculation,  452.  Relation  of  insects  to  the  trans- 
mission of  diseases,  452.  The  food  of  fishes,  452.  The  establish- 
ment and  maintenance  of  biological  laboratories,  452.  The  sta- 
tion at  Naples,  452.  Other  stations,  454.  The  establishment  and 
maintenance  of  technical  periodicals,  454.  Explorations  of  fossil 
records,  455.  The  reconstructive  influence  of  biological  prog- 
ress, 456. 

READING  LIST, 457 

I.  General  References,  451-459.    II.  Special  References,  459-468. 

Index, ,        .  471 


ILLUSTRATIONS 


FIG.  PAGH 

1.  Aristotle,  384-322  b.c, 14 

2.  Pliny,  23-79  a.d., 16 

3.  Galen,  131-200, 25 

4.  VesalIus,  1514-1565,   .* 29 

5.  Anatomical  Sketch  from  Vesalius'  Fahrica  (1543),          .        •  31 

6.  The  Skeleton  from  Vesalius'  Fahrica, 2)2> 

7.  Initial  Letters  from  the  Fahrica, 34 

8.  Fallopius,  1523-1563, 37 

9.  Fabricius,  Harvey's  Teacher,  1537-1619,         .        .        .        -  '^Z 

10.  William  Harvey,  1578-1657, 44 

11.  Scheme  of  the  Portal  Circulation  according  to  Vesalius 

(i543)» 49 

12.  Hooke's  Microscope  (1665), 55 

13.  Malpighi,  1 628-1 694, 59 

14.  From  Malpighi's  Anatomy  oj  the  Silkworm  (1669),     .         .         •  65 

15.  Swammerdam,  1 63 7-1 680, o         .  69 

16.  From  Swammerdam's  Bihlia  Natur-^,  .         .         .         .         -74 

1 7.  Anatomy  of  an  Insect  Dissected  and  Drawn  by  Swammerdam,  76 

18.  Leeuwenhoek,  1632-1723, =79 

19.  Leeuwenhoek's  Microscope, .  82 

20a.  Leeuwenhoek's  Mechanism  for  Examining  the  Circulation 

OF  the  Blood, 8^ 

20b.  The  Capillary  Circulation,  after  Leeuwenhoek,       .        .  84 

21.  Plant  Cells  from  Leeuwenhoek's  Arcana  Natures,         .         .  86 

22.  Lyonet,  1 707-1 789, 90 

23.  Larva  of  the  Willow  Moth,  from  Lyonet's  Monograph 

(1750), 92 

24.  Muscles  of  the  Larva  of  the  Willow  Moth,  from  Lyonet's 

Monograph, 93 

25.  Central  Nervous  System  and  Nerves  of  the  Same  Animal,  93 

26.  Dissection  of  the  Head  of  the  Larva  of  the  Willow  Moth,  94 

27.  The  Brain  AND  Head  Nerves  OF  THE  Same  Animal,  .        .        .95 

28.  roesel  von  rosenhof,  1705-1759,     .....  97 

29.  Reaumur,  1683-175  7,  .  .98 

zxiii 


XXIV  ILLUSTRATIONS 

FIG.  PAGE 

30.  Nervous  System  of  the  Cockchafer,  from  Straus-Durck- 

heim's  Monograph  (1828),      .        .        .        .        .        •        .101 

31.  Ehrenberg,  1795-1876, 108 

32.  Gesner,  1516-1565, 114 

^^.  John  Ray,  1628-1705, 116 

34.  LiNN^us  (1707-17  78)  AT  Sixty, 124 

35.  Karl  Th.  von  Siebold, 13S 

36.  Rudolph  Leuckart, 136 

37.  Severinus,  1580-1656, 142 

38.  Camper,  1772-1789, i44 

39.  John  Hunter,  17 28-1 793, i45 

40.  ViCQ  d'Azyr,  1 748-1 794, 147 

41.  Cuvier  (1769-1829)  as  a  Young  Man, 152 

42.  Cuvier  at  the  Zenith  of  His  Power, 153 

43.  H.  Milne-Edwards,  1800-1885,  .        .        ...        .        -157 

44.  Lacaze-Duthiers,  1821-1901,     .......  159 

45.  Lorenzo  Oken,  1779-1851, 160 

46.  Richard  Owen,  1804-1892,         .        .        .        ...        .        .  161 

47.  J.  Fr.  Meckel,  1781-1833, 162 

48.  Karl  Gegenbaur,  1826-1903, 164 

49.  BicHAT,  1771-1801, 169 

50.  Von  KoellikeRj^'TSi 7-1905, 173 

51.  Rudolph  Virchow,  1821-1903, 174 

52.  Franz  Leydig,  1821-1908 175 

53.  S.  Ramon  y  Cajal, 176 

54.  Albrecht  Haller,  1708-1777, 182 

55.  Charles  Bell,  i 774-1842, 184 

56.  Johannes  Muller,  1801-1858, 187 

57.  Ludwig,  1816-1895, 188 

58.  Du  Bois-Reymond,  1818-1896, 189 

59.  Claude  Bernard,  1813-1878, .        .191 

60.  Frontispiece  of  Harvey's  Generatione  Animalium  (1651),         .  201 

61.  Selected  Sketches  from  Malpighi's  Works,  .        .        .  203 

62.  Marcello  Malpighi,  1 628-1 694, 204 

63.  Plate  from  Wolff's  Theoria  Generationis  (1759),      .         .         .  209 

64.  Charles  Bonnet,  i  720-1793, 212 

65.  Karl  Ernst  von  Baer,  i 792-1876, 216 

66.  Von  Baer  at  about  Seventy  Years  of  Age,   .        .         .        .217 

67.  Sketches  from  Von  Baer's  Embryological  Treatise  (1828),  221 

68.  A.  Kowalevsky,  1840-1901, 225 

69.  Francis  M.  Balfour,  1851-1882, 227 

70.  OSKAR  HeRTWIG  in   189O, 23 1 

71.  WiLHELM  His,  1831-1904, 233 


ILLUSTRATIONS 


XXV 


FIG. 

72. 

73- 

74- 
75- 
76. 

77- 
78. 

79- 
80. 
81. 


82. 

83- 
84. 

85- 
86. 
87. 
88. 
89. 
90. 
91. 

92. 

93. 
94. 

94a 

95- 
96. 

97. 
98. 

99. 
100. 

lOI. 

102. 
103. 
104. 


The  Earliest  Known  Picture  or  Cells,  from  Hooke's  Micro- 
graphia  (1665), 

Sketch  from  Malpighi's  Treatise  on  the  Anatomy  of  Plants 
(1670), 

Theodor  Schwann,  1810-1882, 

M.  ScHLEiDEN,  1 804-1 88 1, 

The  Egg  and  Early  Stages  in  Its  Development  (after  Ge- 
genbaur), 

An  Early  Stage  in  the  Development  of  the  Egg  of  a  Rock 
Limpet  (after  Conklin), 

Highly  Magnified  Tissue-Cells  from  the  Skin  of  a  Sala- 
mander (after  Wilson), 

Diagram  of  the  Chief  Steps  in  Cell-Division  (after  Parker), 

Diagram  of  a  Cell  (modified  after  Wilson), 

{A)  Rotation  OF  Protoplasm  IN  Cells  OF  NiTELLA.  {B)  High- 
ly Magnified  Cells  of  a  Tradescantia  Plant,  Showing 
Circulation  of  Protoplasm  (after  Sedgwick  and  Wilson), 

Felix  Dujardin,  i 801-1860, 

Purkinje,  1 787-1869, 

Carl  Nageli,  181 7-189 i, 

Hugo  von  Mohl,  1805-1872, 

Ferdinand  Cohn,  i  828-1 898, 

Heinrich  Anton  De  Bary,  1831-1888, 

Max  Schultze,  1825-1874, 

Francesco  Redi,  1626-169 7, 

Lazzaro  Spallanzani,  1 729-1799, 

Apparatus  of  Tyndall  for  Experimenting  on  Spontaneous 
Generation,     . ,  290 


238 

239 
245 
246 

253 

254 

255 
256 

257 


261 
265 
267 
268 
269 
271 
272 

280 

283 


Louis  Pasteur  (1822-1895)  and  His  Granddaughter, 
Robert  Koch,  1843-1910, 
Slr  Joseph  Lister,  1827-1912, 
Fritz  Schaudinn,  1871-1906, 
Gregor  Mendel,  1822-1884, 
Francis  Galton,  1822-1911, 
Charles  Lyell,  i 797-1875,   . 
Professor  Owen  and  the  Extinct  Fossil  B 


land,  .... 

Louis  Agassiz,  1807-1873, 
E.  D.  Cope,  1840-1897, 
O.  C.  Marsh,  1831-1899, 
Karl  von  Zittel,  i 839-1 904, 
Transmutations  of  Paludina  (after  Neumayer), 
Planorbis  Shells  from  Steinheim  (after  Hyatt) 


rd  of  New  Zea 


295 
301 
302 

304 
316 

319 

335 
336 
338 
339 
341 
354 
355 


XXVI 


ILLUSTRATIONS 


FIG.  PAGE 

105.  Bones  of  the  Foreleg  of  a  Horse, 358 

106.  Bones  of  Fossil  Ancestors  of  the  Horse,  .         .         .  359 

107.  Representation  of  the  Ancestor  of  the  Horse  Drawn  by 

Charles  R.  Knight  under  the  Direction  of  Professor 
OsBORN.  Permission  of  the  American  Museum  of  Natural 
History, 

108.  Fossil  Remains  of  a  Primitive  Bird  (Arch^opteryx), 

109.  Gill-clefts  of  a  Shark  Compared  with  those  of  the  Em 

bryonic  Chick  and  Rabbit,       ..... 
no.  Jaws  of  an  Embryonic  Whale,  showing  Rudimentary  Teeth,  364 

111.  Profile  Reconstructions  of  the  Skulls  of  Living  and  of 

Fossil  Men, 371 

112.  Lamarck,  i  744-1829, 

113.  Charles  Darwin,  1809-1882, 

114.  August  Weismann,  i  834-1914, 

115.  Hugo  de  Vries,    . 

116.  Buffon,  1 707-1 788, 

117.  Erasmus  Darwin,  i 731-1802, 
108.  Geoffroy  Saint  Hilaire,  i 772-1844, 

119.  Charles  Darwin,  1809-1882, 

120.  Alfred  Russel  Wallace,  1823-1913, 

121.  Thomas  Henry  Huxley,  1825-1895, 

122.  Ernst  Haeckel,  born  1834, 

123.  The  Biological  Station  at  Naples, 


361 
362 

363 


379 
387 
406 
409 
420 
421 
424 
431 
436 
438 
440 

453 


PART    I 

THE    SOURCES    OF    BIOLOGICAL 

IDEAS    EXCEPT    THOSE     OF 

ORGANIC    EVOLUTION 


CHAPTER    I 

AN  OUTLINE  OF  THE  RISE  OF  BIOLOGY  AND   OF 
THE   EPOCHS   IN   ITS   HISTORY 

"Truth  is  the  Daughter  of  Time." 

The  nineteenth  century  will  be  for  all  time  memorable 
for  the  great  extension  of  the  knowledge  of  organic  nature. 
It  was  then  that  the  results  of  the  earlier  efforts  of  mankind 
to  interpret  the  mysteries  of  nature  began  to  be  fruitful; 
observers  of  organic  nature  began  to  see  more  deeply  into 
the  province  of  life,  and,  above  all,  began  to  see  how  to  direct 
their  future  studies.  It  was  in  that  century  that  the  use  of 
the  microscope  made  known  the  similarity  in  cellular  con- 
struction of  all  organized  beings;  that  the  substance,  proto- 
plasm, began  to  be  recognized  as  the  physical  basis  of  life 
and  the  seat  of  all  vital  activities;  then,  most  contagious 
diseases  were  traced  to  microscopic  organisms,  and  as  a  con- 
sequence, medicine  and  surgery  were  reformed;  then  the 
belief  in  the  spontaneous  origin  of  life  under  present  condi- 
tions was  given  up;  and  it  was  in  that  century  that  the 
doctrine  of  organic  evolution  gained  general  acceptance. 
These  and  other  advances  less  generally  known  created  an 
atmosphere  in  which  biology — the  great  life-science — grew 
rapidly. 

In  the  same  period  also  the  remains  of  ancient  life,  long 
since  extinct,  and  for  countless  ages  embedded  in  the  rocks, 
were  brought  to  light,  and  their  investigation  assisted  mate- 
rially in  understanding  the  living  forms  and  in  tracing  their 
genealogy. 

3 


4  BIOLOGY   AND    ITS   MAKERS 

As  a  result  of  these  advances,  animal  organization  began 
to  have  a  different  meaning  to  the  more  discerning  naturalists, 
those  whose  discoveries  began  to  influence  the  trend  of 
thought,  and  finally,  the  idea  which  had  been  so  often  pre- 
viously expressed  became  a  settled  conviction,  that  all  the 
higher  forms  of  life  are  derived  from  simpler  ones  by  a  gradual 
process  of  modification. 

Besides  great  progress  in  biology,  the  nineteenth  century 
was  remarkable  for  similar  advances  in  physics  and  chem- 
istry. Although  these  subjects  purport  to  deal  with  inorganic 
or  lifeless  nature,  they  touch  biology  in  an  intimate  way. 
The  vital  processes  which  take  place  in  all  animals  and  plants 
have  been  shown  to  be  physico-chemical,  and,  as  a  conse- 
quence, one  must  go  to  both  physics  and  chemistry  in  order 
to  understand  them.  The  study  of  organic  chemistry  in  late 
years  has  greatly  influenced  biology;  not  only  have  living 
products  been  analyzed,  but  some  of  them  have  already  been 
constructed  in  the  chemical  laboratory.  The  formation  of 
living  matter  through  chemical  means  is  still  far  from  the 
thought  of  most  chemists,  but  very  complex  organic  com- 
pounds, which  were  formerly  known  only  as  the  result  of 
the  action  of  life,  have  been  produced,  and  the  possibilities 
of  further  advances  in  that  direction  are  very  alluring.  It 
thus  appears  that  the  discoveries  in  various  fields  have 
worked  together  for  a  better  comprehension  of  nature. 

The  Domain  of  Biology. — The  history  of  the  transforma- 
tion of  opinion  in  reference  to  living  organisms  is  an  inter- 
esting part  of  the  story  of  intellectual  development.  The 
central  subject  that  embraces  it  all  is  biology.  This  is  one 
of  the  fundamental  sciences,  since  it  embraces  all  questions 
relating  to  life  in  its  different  phases  and  manifestations. 
Everything  pertaining  to  the  structure,  the  development,  and 
the  evolution  of  living  organisms,  as  well  as  to  their  physiol- 
ogy, belongs  to  biology.     It  is  now  of  commanding  impor- 


OUTLINE    OF    BIOLOGICAL    PROGRESS  5 

tance  in  the  world  of  science,  and  it  is  coming  more  and  more 
to  be  recognized  that  it  occupies  a  field  of  compelling  in- 
terest not  only  for  medical  men  and  scholars,  but  for  all 
intelligent  people.  The  discoveries  and  conquests  of  biology 
have  wrought  such  a  revolution  in  thought  that  they  should 
be  known  to  all  persons  of  liberal  culture.  In  addition  to 
making  acquaintance  with  the  discoveries,  one  ought  to  learn 
something  about  the  history  of  biology;  for  it  is  essential 
to  know  how  it  took  its  rise,  in  order  to  understand  its 
present  position  and  the  nature  of  its  influence  upon  expand- 
ing ideas  regarding  the  world  in  which  we  live. 

In  its  modern  sense,  biology  did  not  arise  until  about 
i860,  when  the  nature  of  protoplasm  was  first  clearly  pointed 
out  by  Max  Schultze,  but  the  currents  that  united  to  form  it 
had  long  been  flowing,  and  we  can  never  understand  the 
subject  without  going  back  to  its  iatric  condition,  when  what 
is  now  biology  was  in  the  germ  and  united  with  medicine. 
Its  separation  from  medicine,  and  its  rise  as  an  independent 
subject,  was  owing  to  the  steady  growth  of  that  zest  for  ex- 
ploration into  unknown  fields  which  began  with  the  new 
birth  of  science  in  the  sixteenth  century,  and  has  continued 
in  fuller  measure  to  the  present.  It  was  the  outcome  of 
applying  observation  and  experiment  to  the  winning  of  new 
truths. 

Difficulties. — But  biology  is  so  comprehensive  a  field, 
and  involves  so  many  details,  that  it  is  fair  to  inquire:  can 
its  progress  be  made  clear  to  the  reader  who  is  unacquainted 
with  it  as  a  laboratory  study  ?  The  matter  will  be  simplified 
by  two  general  observations — first,  that  the  growth  of  biology 
is  owing  to  concurrent  progress  in  three  fields  of  research, 
concerned,  respectively,  with  the  structure  or  architecture  of 
living  beings,  their  development,  and  their  physiology.  We 
recognize  also  a  parallel  advance  in  the  systematic  classifica- 
tion of  animals  and  plants,  and  we  note,  furthermore,  that 


O  BIOLOGY    AND    ITS    MAKERS 

the  idea  of  evolution  permeates  the  whole.  It  will  be  neces- 
sary to  consider  the  advances  in  these  fields  separately,  and 
to  indicate  the  union  of  the  results  into  the  main  channel  of 
progress.  Secondly,  in  attempting  to  trace  the  growth  of  ideas 
in  this  department  of  learning  one  sees  that  there  has  been 
a  continuity  of  development.  The  growth  of  these  notions 
has  not  been  that  of  a  chaotic  assemblage  of  ideas,  but  a 
well-connected  story  in  which  the  new  is  built  upon  the  old 
in  orderly  succession.  The  old  ideas  have  not  been  com- 
pletely superseded  by  the  new,  but  they  have  been  molded 
into  new  forms  to  keep  pace  with  the  advance  of  investigation. 
In  its  early  phases,  the  growth  of  biology  was  slow^  and  dis- 
cursive, but  from  the  time  of  Linnaeus  to  Darwin,  although 
the  details  were  greatly  multiplied,  there  has  been  a  relatively 
simple  and  orderly  progress. 

Facts  and  Ideas. — There  are  many  books  about  biology, 
with  directions  for  laboratory  observation  and  experiment, 
and  also  many  of  the  leading  facts  of  the  science  have  been 
given  to  the  public,  but  an  account  of  the  growth  of  the  ideas, 
which  are  interpretations  of  the  facts,  has  been  rarely  at- 
tempted. From  the  books  referred  to,  it  is  almost  impossible 
to  get  an  idea  of  biology  as  a  unit;  this  even  the  students  in 
our  universities  acquire  only  through  a  coherent  presentation 
of  the  subject  in  the  classroom,  on  the  basis  of  their  work  in 
the  laboratory.  The  critical  training  in  the  laboratory  is 
most  important,  but,  after  all,  it  is  only  a  part,  although  an 
essential  part,  of  a  knowledge  of  biology.  In  general,  too 
little  attention  is  paid  to  interpretations  and  the  drill  is  con- 
fined to  a  few  facts.  Now,  the  facts  are  related  to  the  ideas 
of  the  science  as  statistics  to  history — meaningless  without 
interpretation.  In  the  rise  of  biology  the  facts  have  accu- 
mulated constantly,  through  observation  and  experiment,  but 
the  general  truths  have  emerged  slowly  and  periodically, 
whenever  there  has  been  granted  to  some  mind  an  insight 


OUTLINE    OF    BIOLOGICAL   PROGRESS  7 

into  the  meaning  of  the  facts.     The  detached  facts  are  some- 
times tedious,  the  interpretations  always  interesting. 

The  growth  of  the  knowledge  of  organic  nature  is  a  long 
story,  full  of  human  interest.  Nature  has  been  always  the 
same,  but  the  capacity  of  man  as  its  interpreter  has  varied. 
He  has  had  to  pass  through  other  forms  of  intellectual  activ- 
ity, and  gradually  to  conquer  other  phases  of  natural  phe- 
nomena, before  entering  upon  that  most  difficult  task  of 
investigating  the  manifestations  of  life.  It  will  be  readily 
understood,  therefore,  that  biology  was  delayed  in  its  devel- 
opment until  after  considerable  progress  had  been  made  in 
other  sciences. 

It  is  an  old  saying  that  "Truth  is  the  daughter  of  Time," 
and  no  better  illustration  of  it  can  be  given  than  the  long 
upward  struggle  to  establish  even  the  elemental  truths  of 
nature.  It  took  centuries  to  arrive  at  the  conception  of  the 
uniformity  of  nature,  and  to  reach  any  of  those  generaliza- 
tions which  are  vaguely  spoken  of  as  the  laws  of  nature. 

The  Men  of  Science. — In  the  progress  of  science  there  is 
an  army  of  observers  and  experimenters  each  contributing 
his  share,  but  the  rank  and  file  supply  mainly  isolated  facts, 
while  the  ideas  take  birth  in  the  minds  of  a  few  gifted  leaders, 
either  endowed  with  unusual  insight,  or  so  favored  by  cir- 
cumstances that  they  reach  general  conclusions  of  importance. 
These  advance-guards  of  intellectual  conquest  we  designate 
as  founders.  What  were  they  like  in  appearance?  Under 
what  conditions  did  they  work,  and  what  was  their  chief  aim? 
These  are  interesting  questions  which  will  receive  attention 
as  our  narrative  proceeds. 

A  study  of  the  lives  of  the  founders  shows  that  the  scien- 
tific mood  is  pre-eminently  one  of  sincerity.  The  men  who 
have  added  to  the  growth  of  science  were  animated  by  an 
unselfish  devotion  to  truth,  and  their  lasting  influence  has 
been  in  large  measure  a  reflection  of  their  individual  char- 


8  BIOLOGY   AND    ITS    MAKERS 

acters.  Only  those  have  produced  permanent  residts  who 
have  interrogated  nature  in  the  spirit  of  devotion  to  truth 
and  waited  patiently  for  her  replies.  The  work  founded  on 
selfish  motives  and  vanity  has  sooner  or  later  fallen  by  the 
wayside.  We  can  recognize  now  that  the  work  of  scientific 
investigation,  subjected  to  so  much  hostile  criticism  as  it 
appeared  from  time  to  time,  was  undertaken  in  a  reverent 
spirit,  and  was  not  iconoclastic,  but  remodelling  in  its  in- 
fluence. Some  of  the  glories  of  our  race  are  exhibited  in 
the  lives  of  the  pioneers  in  scientific  progress,  in  their  struggles 
to  establish  some  great  truth  and  to  maintain  intellectual 
integrity. 

The  names  of  some  of  the  men  of  biology,  such  as  Harvey, 
Linnaeus,  Cuvier,  Darwin,  Huxley,  and  Pasteur,  are  widely 
known  because  their  work  came  before  the  people,  but  others 
equally  deserving  of  fame  on  account  of  their  contributions 
to  scientific  progress  will  require  an  introduction  to  most  of 
our  readers. 

In  recounting  the  story  of  the  rise  of  biology,  we  shall 
have  occasion  to  make  the  acquaintance  of  this  goodly  com- 
pany. Before  beginning  the  narrative  in  detail,  however, 
we  shall  look  summarily  at  some  general  features  of  scientific 
progress  and  at  the  epochs  of  biology. 

The  Conditions  under  which  Science  Developed 

In  a  brief  sketch  of  biology  there  is  relatively  little  in  the 
ancient  world  that  requires  notice  except  the  work  of  Aris- 
totle and  Galen;  but  with  the  advent  of  Vesalius,  in  1543, 
our  interest  begins  to  freshen,  and,  thereafter,  through  lean 
times  and  fat  times  there  is  always  something  to  command 
our  attention. 

The  early  conditions  must  be  dealt  with  in  order  to  appre- 
ciate what  followed.     We  are  to  recollect  that  in  the  ancient 


OUTLINE    OF    BIOLOGICAL    PROGRESS  9 

world  there  was  no  science  of  biology  as  such;  nevertheless, 
the  germ  of  it  was  contained  in  the  medicine  and  the  natural 
history  of  those  times. 

There  is  one  matter  upon  which  we  should  be  clear:  in 
the  time  of  Aristotle  nature  was  studied  by  observation  and 
experiment.  This  is  the  foundation  of  all  scientific  ad- 
vancement. Had  conditions  remained  unchanged,  there  is 
reason  to  believe  that  science  would  have  developed  steadily 
on  the  basis  of  the  Greek  foundation,  but  circumstances,  to 
be  spoken  of  later,  arose  which  led  not  only  to  the  complete 
arrest  of  inquiry,  but  also,  the  mind  of  man  being  turned 
away  from  nature,  to  the  decay  of  science. 

Aristotle  the  Founder  of  Natural  History. — The  Greeks 
represented  the  fullest  measure  of  culture  in  the  ancient 
world,  and,  naturally,  we  find  among  them  the  best-developed 
science.  All  the  knowledge  of  natural  phenomena  centered 
in  Aristotle  (384-322  B.C.),  and  for  twenty  centuries  he 
represented  the  highest  level  which  that  kind  of  knowledge 
had  attained. 

It  is  uncertain  how  long  it  took  the  ancient  observers  to 
lift  science  to  the  level  which  it  had  at  the  beginning  of 
Aristotle's  period,  but  it  is  obvious  that  he  must  have  had 
a  long  line  of  predecessors,  who  had  accumulated  facts  of 
observ^ation  and  had  molded  them  into  a  system  before  he 
perfected  and  developed  that  system.  We  are  reminded 
that  all  things  are  relative  when  we  find  Aristotle  referring 
to  the  ancients;  and  well  he  might,  for  we  have  indubitable 
evidence  that  much  of  the  scientific  work  of  antiquity  has 
been  lost.  One  of  the  most  striking  discoveries  pointing 
in  that  direction  is  the  now  famous  papyrus  which  was  found 
by  Georg  Ebers  in  Egypt  about  i860.  The  recent  trans- 
lation of  this  ancient  document  shows  that  it  was  a  treatise 
on  medicine,  dating  from  the  fifteenth  century  B.C.  At  this 
time  the  science  of  medicine  had  attained  an  astonishingly 


lO  BIOLOGY    AND    ITS    MAKERS 

high  grade  of  development  among  that  people.  And  since 
it  is  safe  to  assume  that  the  formulation  of  a  system  of  med- 
icine in  the  early  days  of  mankind  required  centuries  of 
observation  and  practice,  it  becomes  apparent  that  the 
manuscript  in  question  was  no  vague,  first  attempt  at  reduc- 
ing medicine  to  a  system.  It  is  built  upon  much  scientific 
knov^ledge,  and  must  have  been  preceded  by  writings  both 
on  medicine  and  on  its  allied  sciences. 

It  is  not  necessary  that  we  should  attempt  to  picture  the 
crude  beginnings  of  the  observation  of  animated  nature  and 
the  dawning  of  ideas  relative  to  animals  and  plants;  it  is 
suitable  to  our  purpose  to  commence  with  Aristotle,  and  to 
designate  him,  in  a  relative  sense,  as  the  founder  of  natural 
history. 

That  he  was  altogether  dissatisfied  with  the  state  of 
knowledge  in  his  time  and  that  he  had  high  ideals  of  the 
dignity  of  science  is  evidenced  in  his  writings.  Although  he 
refers  to  the  views  of  the  ancients,  he  regarded  himself  in 
a  sense  as  a  pioneer.  "I  found  no  basis  prepared,"  he  says, 
"  no  models  to  copy.  .  .  .  Mine  is  the  first  step,  and  there- 
fore a  small  one,  though  worked  out  with  much  thought 
and  hard  labor.  It  must  be  looked  at  as  a  first  step  and 
judged  with  indulgence."  (From  Osbom's  From  the  Greeks 
to  Darwin.) 

There  is  general  agreement  that  Aristotle  was  a  man  of 
vast  intellect  and  that  he  was  one  of  the  greatest  philosophers 
of  the  ancient  world.  He  has  had  his  detractors  as  w^ell  as 
his  partisan  adherents.  Perhaps  the  just  estimate  of  his 
attainments  and  his  position  in  the  history  of  science  is 
between  the  enthusiastic  appreciation  of  Cuvier  and  the 
critical  estimate  of  Lewes. 

This  great  man  was  born  in  Stagira  in  the  year  384  B.C., 
and  lived  until  322  B.C.  He  is  to  be  remembered  as  the 
most  distinguished  pupil  of  Plato,  and  as  the  instructor  of 


OUTLINE    OF    BIOLOGICAL    PROGRESS  1 1 

Alexander  the  Great.  Like  other  scholars  of  his  time,  he 
covered  a  wide  range  of  subjects;  we  have  mention,  indeed, 
of  about  three  hundred  works  of  his  composition,  many  of 
which  are  lost.  He  wrote  on  philosophy,  metaphysics,  psy- 
chology, politics,  rhetoric,  etc.,  but  it  was  in  the  domain  of 
natural  history  that  he  attained  absolute  pre-eminence. 

His  Position  in  the  Development  of  Science. — It  is  mani- 
festly unjust  to  measure  Aristotle  by  present  standards ;  we 
must  keep  always  in  mind  that  he  was  a  pioneer,  and  that 
he  lived  in  an  early  day  of  science,  when  errors  and  crudities 
were  to  be  expected.  His  greatest  claim  to  eminence  in  the 
history  of  science  is  that  he  conceived  the  things  of  importance 
and  that  he  adopted  the  right  method  in  trying  to  advance 
the  knowledge  of  the  natural  universe.  In  his  program 
of  studies  he  says :  "  First  we  must  understand  the  phenomena 
of  animals;  then  assign  their  causes;  and,  finally,  speak  of 
their  generation."  His  position  in  natural  history  is  fre- 
quently misunderstood.  One  of  the  most  recent  writers  on 
the  history  of  science,  Henry  Smith  Williams,  pictures  him 
entirely  as  a  great  classifier,  and  as  the  founder  of  systematic 
zoology.  While  it  is  true  that  he  was  the  foimder  of  sys- 
tematic zoology,  as  such  he  did  not  do  his  greatest  service 
to  natural  history,  nor  does  the  disposition  to  classify  repre- 
sent his  dominant  activity.  In  all  his  work  classification  is 
made  incidental  and  subservient  to  more  important  considera- 
tions. His  observations  upon  structure  and  development, 
and  his  anticipation  of  the  idea  of  organic  evolution,  are  the 
ones  upon  which  his  great  fame  rests.  He  is  not  to  be  remem- 
bered as  a  man  of  the  type  of  Linnaeus;  rather  is  he  the  fore- 
runner of  those  men  who  looked  deeper  than  Linnaeus  into 
the  structure  and  development  of  animal  life — the  mor- 
j)hologists. 

Particular  mention  of  his  classification  of  animals  will 
be  found  in  the  chapter  on  Linnaeus,  while  in  what  follows 


12  BIOLOGY   AND    ITS    MAKERS 

in  this  chapter  attention  will  be  confined  to  his  observation 
of  their  structure  and  development  and  to  the  general  in- 
fluence of  his  work. 

His  great  strength  was  in  a  philosophical  treatment  of 
the  structure  and  development  of  animals.  Professor  Osborn 
in  his  interesting  book,  From  the  Greeks  to  Darwin^  shows 
that  Aristotle  had  thought  out  the  essential  features  of 
evolution  as  a  process  in  nature.  He  believed  in  a  complete 
gradation  from  the  lowest  organisms  to  the  highest,  and  that 
man  is  the  highest  point  of  one  long  and  continuous  ascent. 

His  Extensive  Knowledge  of  Animals. — He  made  exten- 
sive studies  of  life  histories.  He  knew  that  drone  bees 
develop  without  previous  fertilization  of  the  eggs  (by  par- 
thenogenesis) ;  that  in  the  squid  the  yolk  sac  of  the  embryo 
is  carried  in  front  of  the  mouth;  that  some  sharks  develop 
within  the  egg-tube  of  the  mother,  and  in  some  species  have 
a  rudimentary  blood -connection  resembling  the  placenta  of 
mammals.  He  had  followed  day  by  day  the  changes  in  the 
chick  within  the  hen's  o^gg,  and  observed  the  development  of 
many  other  animals.  In  embryology  also,  he  anticipated 
Harvey  in  appreciating  the  true  nature  of  development  as 
a  process  of  gradual  building,  and  not  as  the  mere  expansion 
of  a  previously  formed  germ.  This  doctrine,  v/hich  is  known 
under  the  name  of  epigenesis,  was,  as  we  shall  see  later, 
hotly  contested  in  the  eighteenth  century,  and  has  a  modified 
application  at  the  present  time. 

In  reference  to  the  structure  of  animals  he  had  described 
the  tissues,  and  in  a  rude  way  analyzed  the  organs  into  their 
component  parts.  It  is  known,  furthermore,  that  he  prepared 
plates  of  anatomical  figures,  but,  unfortunately,  these  have 
been  lost. 

In  estimating  the  contributions  of  ancient  writers  to 
science,  it  must  be  remembered  that  we  have  but  fragments 
of  their  works  to  examine.     It  is,  moreover,  doubtful  whether 


OUTLINE    OF    BIOLOGICAL   PROGRESS  13 

the  scientific  writings  ascribed  to  Aristotle  were  all  from  his 
hand.  The  work  is  so  uneven  that  Huxley  has  suggested 
that,  since  the  ancient  philosophers  taught  viva  voce,  what 
we  have  of  his  zoological  writings  may  possibly  be  the  notes 
of  some  of  his  students.  While  this  is  not  known  to  be  the 
case,  that  hypothesis  enables  us  to  understand  the  intimate 
mixture  of  profound  observation  with  trivial  matter  and 
obvious  errors  that  occur  in  the  writings  ascribed  to  him. 

Hertwig  says:  "It  is  a  matter  for  great  regret  that  there 
have  been  preserved  only  parts  of  his  three  most  important 
zoological  works,  ^  Historia  animalium,^  ^  Dc  partibus,^  and 
'  De  gen  era  Hone, ^  works  in  which  zoology  is  founded  as  a 
universal  science,  since  anatomy  and  embryology,  physiology 
and  classification,  find  equal  consideration." 

Some  Errors. — Dissections  were  little  p)ractised  in  his 
day,  and  it  must  be  admitted  that  his  observations  embrace 
many  errors.  He  supposed  the  brain  to  be  bloodless,  the 
arteries  to  carry  air,  etc.,  but  he  has  been  cleared  by  Huxley 
of  the  mistake  so  often  attributed  to  him  of  supposing  the 
heart  of  mammals  to  have  only  three  chambers.  It  is  alto- 
gether probable  that  he  is  credited  with  a  larger  number  of 
errors  than  is  justified  by  the  facts. 

He  must  have  had  unusual  gifts  in  the  exposition  of  these 
technical  subjects;  indeed,  he  made  his  researches  appear 
so  important  to  his  royal  patron,  Alexander,  that  he  was 
aided  in  the  preparation  of  his  great  Natural  History  by  a 
grant  of  800  talents  (equivalent  to  $200,000)  and  by  nu- 
merous assistants  and  collectors.  Thus  in  ancient  times  was 
anticipated  the  question  that  is  being  agitated  to-day — that 
of  the  support  and  the  endowment  of  research. 

Personal  Appearance. — Some  idea  of  his  looks  may  be 
gained  from  Fig.  i.  This  is  a  copy  of  a  bas-relief  found  in 
the  collection  of  Fulvius  Ursinus  (d.  1600),  and  was  originally 
published  by  J.   Fabcr.     Its  authenticity  as  a  portrait  is 


14 


BIOLOGY   AND    ITS    MAKERS 


attested  (1811)  by  Visconti,  who  says  that  it  has  a  perfect 
resemblance  to  the  head  of  a  small  bust  upon  the  base  of 
which  the  name  of  Aristotle  is  engraved.  Portrait  busts  and 
statues  of  Aristotle  were  common  in  ancient  times.  The 
picture  of  him  most  familiar  to  general  readers  is  the  copy 
of  the  head  and  shoulders  of  an  ancient  statue  representing 
him  with  a  draping  over  the  left   shoulder.     This  is  an 


Fig.   I. — Aristotle,  384-322  B.C. 


attractive  portrait,  showing  a  face  of  strong  intellectuality. 
Its  authenticity,  however,  is  not  as  well  established  as  that 
of  the  picture  shown  here.  Other  pictures,  believed  to  be 
those  of  Aristotle,  represent  him  later  in  life  with  receding 
hair,  and  one  exists  in  which  his  baldness  is  very  extensive. 
He  was  described  as  short  in  stature,  with  spindling  legs  and 
small,  penetrating  eyes,  and  to  have  been,  in  his  younger 
days,  vain  and  showy  in  his  dress. 


OUTLINE    OF    BIOLOGICAL    PROGRESS  ^5 

He  was  early  left  an  orphan  with  a  considerable  fortune; 
and  there  are  stories  of  early  excesses  after  coming  into  his 
property.  These  charges,  however,  lack  trustworthy  support, 
and  are  usually  regarded  as  due  mainly  to  that  under- 
mining gossip  which  follows  one  holding  prominent  place 
and  enviable  recognition.  His  habits  seem  to  have  been 
those  of  a  diligent  student  Vv^ith  a  zest  in  his  work;  he  was  an 
omnivorous  reader,  and  Plato  called  him  the  mind  of  his 
school.  His  large  private  library  and  his  manner  of  liv- 
ing bespeak  the  conserving  of  his  property,  rather  than  its 
waste  in  selfish  indulgences. 

His  Influence. — The  influence  of  Aristotle  was  in  the 
right  direction.  He  made  a  direct  appeal  to  nature  for  his 
facts,  and  founded  his  Natural  History  only  on  observation 
of  the  structure,  physiology,  and  development  of  animals. 
Unfortunately,  the  same  cannot  be  said  of  his  successors. 

Galen,  who  is  mentioned  above  in  connection  with  Aris- 
totle, was  a  medical  writer  and  the  greatest  anatomist  of 
antiquity.  On  account  of  the  relation  of  his  work  to  the 
growth  of  anatomy,  however,  the  consideration  of  it  is  re- 
served for  the  chapter  on  Vesalius. 

Soon  after  the  period  of  Aristotle  the  center  of  scientific 
investigation  was  transferred  to  Alexandria,  where  Ptolemy 
had  erected  a  great  museum  and  founded  a  large  public 
library.  Here  mathematics  and  geography  flourished,  but 
natural  history  was  little  cultivated. 

In  order  to  find  the  next  famous  naturalist  of  antiquity, 
it  is  necessary  to  look  to  Rome.  Rome,  although  great  in 
political  power,  never  became  a  true  culture  center,  char- 
acterized by  originality.  All  that  remains  of  their  thought 
shows  us  that  the  Roman  people  were  not  creative.  In  the 
capital  of  the  empire,  the  center  of  its  life,  there  arose  no 
great  scientific  investigator. 

Pliny. — The  situation  is  represented  by  Pliny  the  Elder 


1(5 


BIOLOGY   AND    ITS    MAKERS 


(23-79  A.D.),  the  Roman  general  and  litterateur  (Fig.  2). 
His  works  on  natural  history,  filling  thirty-seven  volumes, 
have  been  preserved  with  greater  completeness  than  those  of 
other  ancient  writers.  Their  overwhelming  bulk  seems  to 
have  produced  an  impression  upon  those  who,  in  the  nine- 
teenth century,  heralded  him  as  the  greatest  naturalist  of 


Fig.  2. — Pliny,  23-79  a.d. 

antiquity.  But  an  examination  of  his  writings  shows  that 
he  did  nothing  to  deepen  or  broaden  the  knowledge  of  nature, 
and  his  Natural  History  marks  a  distinct  retrograde  movement. 
He  was,  at  best,  merely  a  compiler — "  sl  collector  of  anec- 
dotes " — who,  forsaking  observation,  indiscriminately  mixed 
fable,  fact,  and  fancy  taken  from  the  writings  of  others. 
He  emphasized  the  feature  of  classification  which  Aristotle 
had  held  in  proper  subordination,  and  he  replaced  the  clas- 


OUTLINE    OF    BIOLOGICAL    PROGRESS  I? 

sification  of  Aristotle,  founded  on  plan  of  organization,  by  a 
highly  artificial  one,  founded  on  the  incidental  circumstance 
6f  the  abodes  of  animals — either  in  air,  water,  or  on  the  earth. 

The  Arrest  of  Inquiry  and  its  Effects. — Thus,  natural 
history,  transferred  from  a  Greek  to  a  Roman  center,  was 
already  on  the  decline  in  the  time  of  Pliny;  but  it  was  des- 
tined to  sink  still  lower.  It  is  an  old,  oft-repeated  story  how, 
with  the  overthrow  of  ancient  civilization,  the  torch  of  learn- 
ing was  nearly  extinguished.  Not  only  was  there  a  complete 
political  revolution ;  there  was  also  a  complete  change  in  the 
mental  interests  of  mankind.  The  situation  is  so  complex 
that  it  is  difficult  to  state  it  with  clearness.  So  far  as  science 
is  concerned,  its  extinction  was  due  to  a  turning  away  from 
the  external  world,  and  a  complete  arrest  of  inquiry  into  the 
phenomena  of  nature.  This  was  an  important  part  of  that 
somber  change  which  came  over  all  mental  life. 

One  of  the  causes  that  played  a  considerable  part  in  the 
cessation  of  scientific  investigation  was  the  rise  of  the  Chris- 
tian church  and  the  dominance  of  the  priesthood  in  all  intellec- 
tual as  well  as  in  spiritual  life.  The  world  shunning  spirit, 
so  scrupulously  cultivated  by  the  early  Christians,  prompted 
a  spirit  which  was  hostile  to  observation.  The  behest  to 
shun  the  world  was  acted  upon  too  literally.  The  eyes  were 
closed  to  nature  and  the  mind  was  directed  tov/ard  spiritual 
matters,  which  truly  seemed  of  higher  importance.  Pres- 
ently, the  observation  of  nature  came  to  be  looked  upon  as 
proceeding  from  a  prying  and  impious  curiosity. 

Books  were  now  scarcer  than  during  the  classical  period ; 
the  schools  of  philosophy  were  reduced,  and  the  dissemina- 
tion of  learning  ceased.  The  priests  who  had  access  to  the 
books  assumed  direction  of  intellectual  life.  But  they  were 
largely  employed  with  the  analysis  of  the  supernatural, 
without  the  wholesome  check  of  observation  and  experiment ; 
mystical  explanations  were  invented  for  natural  phenomena, 


.l8  BIOLOGY    AND    ITS    MAKERS 

while  metaphysical  speculation  became  the  dominant  form 
of  mental  activity. 

Authority  Declared  the  Source  of  Knowledge. — In  this 
atmosphere  controversies  over  trivial  points  were  engendered, 
and  the  ancient  writings  were  quoted  as  sustaining  one  side 
or  the  other.  All  this  led  to  the  referring  of  questions  as  to 
their  truth  or  error  to  authority  as  the  source  of  knowledge, 
and  resulted  in  a  complete  eclipse  of  reason.  Amusing  illus- 
trations of  the  situation  are  abundant;  as  when,  in  the 
Middle  Ages,  the  question  of  the  number  of  teeth  in  the  horse 
was  debated  with  great  heat  in  many  contentious  writings. 
Apparently  none  of  the  contestants  thought  of  the  simple 
expedient  of  counting  them,  but  tried  only  to  sustain  their 
position  by  reference  to  authority.  Again,  one  who  noticed 
spots  on  the  sun  became  convinced  of  the  error  of  his  eyes 
because  Aristotle  had  somewhere  written  "The  face  of  the 
sun  is  immaculate." 

This  was  a  barren  period  not  only  for  science,  but  also 
for  ecclesiastical  advance.  Notwithstanding  the  fact  that 
for  more  than  a  thousand  years  the  only  new  works  were 
written  by  professional  theologians,  there  was  no  substantial 
advance  in  their  field,  and  we  cannot  escape  the  reflection 
that  the  reciprocal  action  of  free  inquiry  is  essential  to  the 
growth  of  theology  as  of  other  departments  of  learning. 

In  the  period  from  the  downfall  of  Rome  to  the  revival 
of  learning,  one  eminent  theologian,  St.  Augustine,  stands 
in  relief  for  the  openness  of  his  mind  to  new  truth  and  for 
his  expressions  upon  the  relation  of  revelation  in  the  Scrip- 
tures to  the  observation  of  nature.  His  position  will  be  more 
clearly  indicated  in  the  chapter  dealing  with  the  rise  of 
evolutionary  thought. 

Perhaps  it  has  been  the  disposition  of  historians  to  paint 
the  Middle  Ages  in  too  dark  colors  in  order  to  provide  a 
background  on  which  fitly  to  portray  the  subsequent  awak- 


OUTLINE    OF    BIOLOGICAL   PROGRESS  19 

ening.  It  was  a  remolding  period  through  which  it  was 
necessary  to  pass  after  the  overthrow  of  ancient  civilization 
and  the  mixture  of  the  less  advanced  people  of  the  North  with 
those  of  the  South.  The  opportunities  for  advance  were 
greatly  circumscribed ;  the  scarcity  of  books  and  the  lack  of 
facilities  for  travel  prevented  any  general  dissemination  of 
learning,  while  the  irresponsible  method  of  the  time,  of 
appealing  to  authority  on  all  questions,  threw  a  barrier  across 
the  stream  of  progress.  Intellectuality  was  not,  however, 
entirely  crushed  during  the  prevalence  of  these  conditions. 
The  medieval  philosophers  were  masters  of  the  metaphysical 
method  of  argument,  and  their  mentality  was  by  no  means 
dull.  While  some  branches  of  learning  might  make  a  little 
advance,  the  study  of  nature  suffered  the  most,  for  the  knowl- 
edge of  natural  phenomena  necessitates  a  mind  turned 
outward  in  direct  observation  of  the  phenomena  of  the 
natural  and  physical  universe. 

Renewal  of  Observation. — It  was  an  epoch  of  great  im- 
portance, therefore,  when  men  began  again  to  observe,  and 
to  attempt,  even  in  an  unskilful  way,  hampered  by  intellec- 
tual inheritance  and  habit,  to  unravel  the  mysteries  of  nature 
and  to  trace  the  relation  between  causes  and  effects  in  the 
universe.  This  new  movement  was  a  revolt  of  the  intellect 
against  existing  conditions.  In  it  were  locked  up  all  the 
benefits  that  have  accrued  from  the  development  of  modern 
science.  Just  as  the  decline  had  been  due  to  many  causes, 
so  also  the  general  revival  was  complex.  The  invention  of 
printing,  the  voyages  of  mariners,  the  rise  of  universities, 
and  the  circulation  of  ideas  consequent  upon  the  Crusades, 
all  helped  to  disseminate  the  intellectual  ferment.  These 
generic  influences  aided  in  molding  the  environment,  but, 
just  as  the  pause  in  science  had  been  due  to  the  turning  away 
from  nature  and  to  new  mental  interests,  so  the  revival  was 
a  return  to  nature  and  to  the  method  of  science.     The  pio- 


20  BIOLOGY    AND    ITS    MAKERS 

neers  had  to  be  men  of  determined  independence;  they  labored 
against  self-interest  as  well  as  opposition  from  the  church 
and  the  priesthood,  and  they  withstood  the  terrors  of  the 
Inquisition  and  the  loss  of  recognition  and  support. 

In  this  uncongenial  atmosphere  men  like  Galileo,  Des- 
cartes, and  Vesalius  established  the  new  movement  and  over- 
threw the  reign  of  authority.  With  the  coming  of  \'esalius 
the  new  era  of  biological  progress  w^as  opened,  but  its  growth 
was  a  slow  one;  a  growth  of  which  we  are  now  to  be  con- 
cerned in  tracing  the  main  features. 

Forecast  of  Biological  History 

It  will  be  helpful  to  outline  the  epochs  of  biological  prog- 
ress before  taking  them  up  for  fuller  consideration.  The 
foundation  of  progress  was  the  renewal  of  observation  in 
which,  as  already  stated,  all  modern  science  was  involved. 

It  was  an  epoch  in  biological  history  .when  Vesalius  (1514- 
1564)  overthrew  the  authority  of  Galen,  and  ^tudied  at  first 
hand  the  organization  of  the  human  body. 

It  was  an  epoch  when  William  Harvey  (1578-1667),  by 
adding  experiment  to  observation,  demonstrated  the  circula- 
tion of  the  blood  and  created  a  new  physiology.  The  two 
coordinate  branches  of  biology  were  thus  early  outlined. 

The  introduction  of  the  microscope  in  the  seventeenth 
century,  mainly  through  the  labors  of  Grew,  Hooke,  Mal- 
pighi,  and  Leeuwenhoek,  opened  a  new  world  to  the  investi- 
gator, and  the  work  of  these  men  marks  an  epoch  in  the  prog- 
ress of  independent  inquiry. 

Linnaeus  (i 707-1 778),  by  introducing  short  descriptions 
and  uniform  names  for  animals  and  plants,  greatly  advanced 
the  subject  of  natural  history. 

Cuvier  (1769-183  2),  by  founding  the  school  of  compara- 


OUTLINE   OF   BIOLOGICAL   PROGRESS  21 

live  anatomy,  so  furthered  the  knowledge  of  the  organization 
of  animals  that  he  created  an  epoch. 

Bichat  (1771-1801)  his  great  contemporary,  created  an- 
other by  laying  the  foundation  of  our  knowledge  of  the  struc- 
ture of  animal  tissues. 

Von  Baer  (1792-1876),  by  his  studies  of  the  development 
of  animal  life,  supplied  what  was  lacking  in  the  work  of 
Cuvier  and  Bichat  and  originated  modern  embryology. 

Haller  (i 708-1 777),  in  the  eighteenth,  and  Johannes  Miil- 
ler  (1801-1858)  in  the  nineteenth  century,  so  added  to  the 
ground  work  of  Harvey  that  physiology  was  made  an  inde- 
pendent subject  and  was  established  on  modern  lines. 

With  Buff  on,  Erasmus,  Darwin,  and  Lamarck  (1744- 
1829)  began  an  epoch  in  evolutionary  thought  which  had 
its  culminating  point  in  the  work  of  Charles  Darwin  (1869- 
1882). 

Mendel's  experimental  observations  on  inheritance,  pub- 
lished in  1866,  mark  one  of  the  most  important  biological 
discoveries  of  the  nineteenth  century,  although  the  recogni- 
tion of  his  work  was  delayed  till  the  year  1901. 

After  Cuvier  and  Bichat  came  the  estabhshing  of  the  cell- 
theory  (1838),  which  created  an  epoch  and  influenced  all 
further  progress. 

Finally,  through  the  discovery  of  protoplasm  (1835)  and 
the  recognition  that  it  is  the  seat  of  all  vital  activity,  arrived 
the  epoch  (1861)  which  brought  us  to  the  threshold  of  the 
biology  of  the  present  day. 

Step  by  step  naturalists  have  been  led  from  the  obvious  and 
superficial  facts  about  living  organisms  to  the  deeplying 
basis  of  all  vital  manifestations. 


CHAPTER    II 

VESALIUS  AND  THE  OVERTHROW  OF   AUTHORITY 
IN   SCIENCE 

Vesalius,  although  an  anatomist,  is  to  be  recognized  in  a 
broad  sense  as  one  of  the  founders  of  biology.  When  one 
is  attempting  to  investigate  animal  and  plant  life,  not  only 
must  he  become  acquainted  with  the  external  appearance  of 
living  organisms,  but  also  must  acquire  early  a  knowledge 
of  their  structure,  without  which  other  facts  relating  to  their 
lives  can  not  be  disclosed.  Anatomy,  which  is  the  science 
of  the  structure  of  organized  beings,  is  therefore  so  funda- 
mental that  we  find  ourselves  involved  in  tracing  the  history 
of  its  rise  as  one  part  of  the  story  of  biology.  But  it  is  not 
enough  to  know  how  animals  and  plants  are  constructed; 
we  must  also  know  something  about  the  purpose  of  the 
structures  and  of  the  life  that  courses  through  them,  and, 
accordingly,  after  considering  the  rise  of  anatomy,  we  must 
take  a  similar  view  of  its  counterpart,  physiology. 

The  great  importance  of  Vesalius  in  the  history  of  science 
lies  in  the  fact  that  he  overthrew  adherence  to  authority  as 
the  method  of  ascertaining  truth,  and  substituted  therefor 
observation  and  reason.  Several  of  his  forerunners  had 
tried  to  accomplish  the  same  end,  but  they  had  failed.  He 
was  indebted  to  them  as  every  man  is  indebted  to  his  fore- 
bears, but  at  the  same  time  we  can  not  fail  to  see  that  Vesalius 
was  worthy  of  the  victory.  He  was  more  resolute  and  force- 
ful than  any  of  his  predecessors.     He  was  one  of  those  rare 


OVERTHROW    OF    AUTHORITY    IN    SCIENCE        23 

Spirits  who  see  new  truth  wdth  clearness,  and  have  the  bravery 
to  force  their  thoughts  on  an  unsympathetic  public. 

The  Beginning  of  Anatomy. — In  order  to  appreciate  his 
service  it  is  necessary  to  give  a  brief  account  of  his  predeces- 
sors, and  of  the  condition  of  anatomy  in  his  time.  Remem- 
bering that  anatomy  embraces  a  knov/ledge  of  the  architec- 
ture of  all  animals  and  plants,  we  can,  nevertheless,  see  why 
in  early  times  it  should  have  had  more  narrow  boundaries. 
The  m.edical  men  were  the  first  to  take  an  interest  in  the 
structure  of  the  human  body,  because  a  knowledge  of  it  is 
necessary  for  medicine  and  surgery.  It  thus  happens  that 
the  earliest  observations  in  anatomy  were  directed  toward 
making  known  the  structure  of  the  human  body  and  that  of 
animals  somewhat  closely  related  to  man  in  point  of  struc- 
ture. Anatomical  studies,  therefore,  began  with  the  more 
complex  animals  instead  of  the  simpler  ones,  and,  later, 
when  comparative  anatomy  began  to  be  studied,  this  led  to 
many  misunderstandings ;  since  the  structure  of  man  became 
the  type  to  which  all  others  were  referred,  while,  on  account 
of  his  derivation,  his  structure  presents  the  greatest  modifi- 
cation of  the  vertebrate  type. 

It  was  so  difficult  in  the  early  days  to  get  an  opportunity 
to  study  the  human  body  that  the  pioneer  anatomists  were 
obliged  to  gain  their  knowledge  by  dissections  of  animals,  as 
the  dog,  and  occasionally  the  monkey.  In  this  way  Aristotle 
and  his  forerunners  learned  much  about  anatomy.  About 
300  B.C.,  the  dissection  of  the  human  body  was  legalized  in 
the  Alexandrian  school,  the  bodies  of  condemned  criminals 
being  devoted  to  that  purpose.  But  this  did  not  become 
general  even  for  medical  practitioners,  and  anatomy  contin- 
ued to  be  studied  mainly  from  brute  animals. 

Galen. — The  anatomist  of  antiquity  who  outshines  all 
others  was  Galen  (Claudius  Galenus,  130-200  a.d.),  who  lived 
some  time  in  Pergamos,  and  for  five  years  in  Rome,  during 


24  BIOLOGY   AND    ITS    MAKERS 

the  second  century  of  the  Christian  era.  He  was  a  man  of 
much  talent,  both  as  an  observer  and  as  a  writer.  His  de- 
scriptions were  clear  and  forceful,  and  for  twelve  centuries 
his  works  exerted  the  greatest  influence  of  those  of  all  scien- 
tific writers.  In  his  wTitings  was  gathered  all  the  anatomical 
knowledge  of  his  predecessors,  to  which  he  had  added  ob- 
servations of  his  own.  He  was  a  man  of  originality,  but  not 
having  the  human  body  for  dissection,  he  erred  in  expounding 
its  structure  "on  the  faith  of  observations  made  on  lower 
animals,"  He  used  the  right  method  in  arriving  at  his  facts. 
Huxley  says:  " No  one  can  read  Galen's  works  without  being 
impressed  with  the  marvelous  extent  and  diversity  of  his 
knowledge,  and  by  his  clear  grasp  of  those  experimental 
methods  by  which  alone  physiology  can  be  advanced." 

Anatomy  in  the  Middle  Ages. — But  now  we  shall  see  how 
the  arrest  of  inquiry  already  spoken  of  operated  in  the  field 
of  anatomy.  The  condition  of  anatomy  in  the  Middle  Ages 
was  the  condition  of  all  science  in  the  same  period.  From 
its  practical  importance  anatomy  had  to  be  taught  to  medical 
men,  while  physics  and  chemistry,  biology  and  comparative 
anatomy  remained  in  an  undeveloped  state.  The  way  in 
which  this  science  was  taught  is  a  feature  which  characterizes 
the  intellectual  life  of  the  Middle  Ages.  Instead  of  having 
anatomy  taught  by  observations,  the  writings  of  Galen  were 
expounded  from  the  desk,  frequently  without  demonstrations 
of  any  kind.  Thus  his  work  came  to  be  set  up  as  the  one 
unfailing  authority  on  anatomical  knowledge.  This  was  in 
accord  with  the  dominant  ecclesiastical  influence  of  the  time. 
Reference  to  authority  w^as  the  method  of  the  theologians, 
and  by  analogy  it  became  the  method  of  all  learning.  As 
the  Scriptures  v/ere  accepted  as  the  unfailing  guide  to  spir- 
itual truth,  so  Galen  and  other  ancient  writers  were  made 
the  guides  to  scientific  truth  and  thought.  The  baneful 
effects  of  this  in  stifling  inquiry  and  in  reducing  knowledge 


Fig.  3. — Galen,   131-200. 
From  Acta  Medicorvm  Berolinensium,  1715. 


26  BIOLOGY   AND    ITS    MAKERS 

to  parrot-like  repetition  of  ancient  formulas  are  so  obvious 
that  they  need  not  be  especially  dwelt  upon. 

Predecessors  of  Vesalius. — Italy  gave  birth  to  the  first 
anatomists  who  led  a  revolt  against  this  slavery  to  authority 
in  scientific  matters.  Of  the  eminent  anatomists  who  pre- 
ceded Vesalius  it  will  be  necessary  to  mention  only  three. 
Mundinus,  or  Mondino,  professor  at  the  University  of 
Bologna,  who,  in  the  early  part  of  the  fourteenth  century, 
dissected  three  bodies,  published  in  131 5  a  work  founded 
upon  human  dissection.  He  was  a  man  of  originality  whose 
work  created  a  sensation  in  the  medical  world,  but  did  not 
supersede  Galen's.  His  influence,  although  exerted  in  the 
right  direction,  was  not  successful  in  establishing  observation 
as  the  method  of  teaching  anatomy.  His  book,  however, 
was  sometimes  used  as  an  introduction  to  Galen's  writings 
or  in  conjunction  with  them. 

The  next  man  who  requires  notice  is  Berengarius  of  Carpi, 
who  was  a  professor  in  the  University  of  Bologna  in  the  early 
part  of  the  sixteenth  century.  He  is  said  to  have  dissected 
not  less  than  one  hundred  human  bodies ;  and  although  his 
opportunities  for  practical  study  were  greater  than  those  of 
Mondino,  his  attempts  to  place  the  science  of  anatomy  upon 
a  higher  level  were  also  unsuccessful. 

We  pass  now  from  Italy  to  France  where  Jacobus  Sylvius 
(1478-1555),  one  of  the  teachers  of  Vesalius,  became  distin- 
guished as  a  teacher  of  anatomy.  The  work  of  this  man  has 
been  confused  with  that  of  Franciscus  Sylvius  (16 14-167 2), 
who  lived  about  a  century  later  in  Holland.  The  recent 
analysis  of  the  original  sources  by  Dr.  Frank  Baker  has 
served  to  clear  away  many  misconceptions  regarding  the 
two  Sylviuses.  Jacobus  Sylvius  did  not  investigate  the 
brain  nor  were  the  fissure  and  artery  of  Sylvius  named  in  his 
honor.  On  the  contrary,  Franciscus  Sylvius  described  these 
parts  for  the  first  time,  about  1641,  and  they  bear  his  name. 


OVERTHROW  OF  AUTHORITY  IN  SCIENCE  27 

The  historical  association  of  Jacobus  Sylvius  with  Vesalius 
makes  it  of  prime  importance  to  do  justice  to  his  services  to 
anatomy,  more  especially  since  Vesalius  made  indiscriminate 
criticisms  of  his  teacher  that  have  generally  been  accepted 
without  further  testimony.  Jacobus  Sylvius  evidently  under- 
stood what  was  essential  to  a  reform  in  the  teaching  of  anat- 
omy, for,  in  his  introduction  to  anatomy,  he  is  very  explicit 
in  advising  that  the  study  be  pursued  always  by  eye  and 
touch  and  primarily  from  the  human  body.  He  says  that 
anatomy  can  never  be  taught  by  reading  and  description. 
Nevertheless,  the  limitations  under  which  he  labored,  the 
lack  of  sufficiently  strong  initiative,  and  the  practical  diffi- 
culty of  obtaining  material,  led  him  to  teach  the  subject  on 
a  lower  level  than  he  theoretically  advocated.  He  read  Galen 
to  his  classes  and  the  limited  number  of  dissections  in  his 
lecture  room  were  made  usually  on  the  bodies  of  dogs  by 
unskilled  barbers.  With  all  these  limitations,  he  helped 
to  elevate  the  standard  of  teaching  anatomy  in  France,  he 
was  very  clear  as  an  expounder  of  the  subject,  and  he  made 
an  important  contribution  in  assigning  special  names  to 
muscles  and  bloodvessels.  Galen  had  designated  muscles 
and  other  parts  by  numbers,  while  Vesalius  gave  them  spe- 
cific names,  some  of  which  are  in  use  today.  He  was  such  a 
worshipper  of  Galen  that  his  method  was  essentially  that  of 
authority  and  the  progress  of  science  awaited  an  innovator. 

Vesalius. — Vesalius  now  came  upon  the  scene;  and 
through  his  efforts,  before  he  was  thirty  years  of  age,  the  idol 
of  authority  had  been  shattered,  and,  mainly  through  his 
persistence,  the  method  of  so  great  moment  to  future  ages 
had  been  established.  He  was  well  fitted  to  do  battle  against 
tradition — strong  in  body,  in  mind,  and  in  purpose,  gifted 
and  forceful;  and,  furthermore,  his  work  was  marked  by 
concentration  and  by  the  high  moral  quahty  of  fidelity  to 
truth. 


28  BIOLOGY   AND    ITS    MAKERS 

Vesalius  was  bom  in  Brussels  on  the  last  day  of  the  year 
1 514,  of  an  ancestry  of  physicians  and  learned  men,  from 
whom  he  inherited  his  leaning  toward  scientific  pursuits. 
Early  in  hfe  he  exhibited  a  passion  for  anatomy;  he  dissected 
birds,  rabbits,  dogs,  and  other  animals.  Although  having 
a  strong  bent  in  this  direction,  he  was  not  a  man  of  single 
talent.  He  was  schooled  in  all  the  learning  of  his  time, 
and  his  earliest  publication  was  a  translation  from  the  Greek 
of  the  ninth  book  of  Rhazes.  After  his  early  training  at 
Brussels  and  at  the  University  of  Louvain,  in  1533,  at  the 
age  of  18,  he  went  to  Paris  to  study  medicine,  where,  in 
anatomy,  he  came  under  Sylvius  and  Giinther. 

His  Force  and  Independence. — His  impetuous  nature  was 
shown  in  the  amphitheatre  of  Sylvius,  where,  at  the  third 
lecture,  he  pushed  aside  the  clumsy  surgeon  barbers,  and 
himself  exposed  the  parts  as  they  should  be.  He  could  not 
be  satisfied  with  the  exposition  of  the  printed  page ;  he  must 
see  with  his  own  eyes,  must  grasp  through  his  own  expe- 
rience the  facts  of  anatomical  structure.  This  demand  of 
his  nature  shows  not  only  how  impatient  he  was  with 
sham,  but  also  how  much  more  he  was  in  touch  with  reality 
than  were  the  men  of  his  time. 

After  three  years  at  the  French  capital,  owing  to  wars 
in  Belgium,  he  went  back  to  Louvain  without  obtaining  his 
medical  degree.  After  a  short  experience  as  surgeon  on  the 
field  of  battle,  he  went  to  Padua,  whither  he  was  attracted 
by  reports  of  the  opportunities  for  practical  dissection  that 
he  so  much  desired  to  undertake.  There  his  talents  were 
recognized,  and  just  after  receiving  his  degree  of  Doctor  of 
Medicine  in  1537,  he  was  given  a  post  in  surgery,  with  the 
care  of  anatomy,  in  the  university. 

His  Reform  of  the  Teaching  of  Anatomy. — The  sympa- 
thetic and  graphic  description  of  this  period  of  his  career  by 
Sir  Michael  Foster  is  so  good  that  I  can  not  refrain  from 


Fig.  4. — Vesalius,  15 14-1564. 


30  BIOLOGY   AND    ITS    MAKERS 

quoting  it:  "He  at  once  began  to  teach  anatomy  in  his  own 
new  way.  Not  to  unskilled,  ignorant  barbers  would  he  en- 
trust the  task  of  laying  bare  before  the  students  the  secrets  of 
the  human  frame;  his  own  hand,  and  his  own  hand  alone, 
was  cunning  enough  to  track  out  the  pattern  of  the  structures 
which  day  by  day  were  becoming  more  clear  to  him.  Fol- 
lowing venerated  customs,  he  began  his  academic  labors  by 
*  reading'  Galen,  as  others  had  done  before  him,  using  his 
dissections  to  illustrate  what  Galen  had  said.  But,  time  after 
time,  the  body  on  the  table  said  something  different  from 
that  which  Galen  had  written. 

''He  tried  to  do  what  others  had  done  before  him — he 
tried  to  believe  Galen  rather  than  his  own  eyes,  but  his  eyes 
were  too  strong  for  him;  and  in  the  end  he  cast  Galen  and 
his  writings  to  the  winds,  and  taught  only  what  he  himself 
had  seen  and  what  he  could  make  his  students  see,  too. 
Thus  he  brought  into  anatomy  the  new  spirit  of  the  time,, 
and  the  men  of  the  time,  the  young  men  of  the  time,  answered 
the  new  voice.  Students  flocked  to  his  lectures;  his  hearers 
amounted,  it  is  said,  to  some  five  hundred,  and  an  enlightened 
senate  recognized  his  worth  by  repeatedly  raising  his  emol- 
uments. 

"Five  years  he  thus  spent  in  untiring  labors  at  Padua. 
Five  years  he  wrought,  not  weaving  a  web  of  fancied  thought, 
but  patiently  disentangling  the  pattern  of  the  texture  of 
the  human  body,  trusting  to  the  words  of  no  master,  ad- 
mitting nothing  but  that  which  he  himself  had  seen;  and  at 
the  end  of  the  five  years,  in  1542,  while  he  was  as  yet  not 
twenty-eight  years  of  age,  he  was  able  to  write  the  dedi- 
cation to  Charles  V  of  a  folio  work  entitled  the  '  Structure  of 
the  Human  Body,'  adorned  with  many  plates  and  woodcuts 
which  appeared  at  Basel  in  the  following  year,  1543." 

His  Physiognomy. — This  classic  with  the  Latin  title, 
De  Humani  Corporis  Fabrica,  requires  some  special  notice;. 


Fig.   5. — Anatomical  Sketch  from  Vesalius's  Fabrica. 
(Photographed  and  reduced  from  the  facsimile  edition  of  1728.) 


32  BIOLOGY   AND    ITS    MAKERS 

but  first  let  us  have  a  portrait  of  Vesalius,  the  master.  Fig.  4 
shows  a  reproduction  of  the  portrait  with  which  his  work 
is  provided.  He  is  represented  in  academic  costume,  prob- 
ably that  which  he  wore  at  lectures,  in  the  act  of  demonstrat- 
ing the  muscles  of  the  arm.  The  picture  is  reduced,  and  in 
the  reduction  loses  something  of  the  force  of  the  original. 
We  see  a  strong,  independent,  self-willed  countenance;  what 
his  features  lack  in  refinement  they  make  up  in  force ;  not 
an  artistic  or  poetic  face,  but  the  face  of  the  man  of  action 
with  scholarly  training. 

His  Great  Book. — The  book  of  Vesalius  laid  the  founda- 
tion of  modern  biological  science.  It  is  more  than  a  land- 
mark in  the  progress  of  science — it  created  an  epoch.  It  is 
not  only  interesting  historically,  but  on  account  of  the  highly 
artistic  plates  with  which  it  is  illustrated  it  is  interesting  to 
examine  by  one  not  an  anatomist.  For  executing  the  plates 
Vesalius  secured  the  service  of  a  fellow-countryman,  John 
Stephen  de  Calcar,  who  was  one  of  the  most  gifted  pupils  of 
Titian.  The  drawings  are  of  such  high  artistic  quality  that 
for  a  long  time  they  were  ascribed  to  Titian.  The  artist  has 
attempted  to  soften  the  necessarily  prosaic  nature  of  anatom- 
ical illustrations  by  introducing  an  artistic  background  of 
landscape  of  varied  features,  with  bridges,  roads,  streams, 
buildings,  etc.  The  employment  of  a  background  even  in 
portrait-painting  was  not  uncommon  in  the  same  century, 
as  in  Leonardo  da  Vinci's  well-known  Mona  Lisa,  with  its 
suggestive  perspective  of  water,  rocks,  etc. 

Fig.  5  will  give  an  idea  on  a  small  scale  of  one  of  the  plates 
illustrating  the  work  of  Vesalius.  The  plates  in  the  original 
are  of  folio  size,  and  represent  a  colossal  figure  in  the  fore- 
ground, with  a  background  showing  between  the  limbs  and 
at  the  sides  of  the  figure.  There  is  considerable  variety  as 
regards  the  background,  no  two  plates  being  alike. 

Also,  in  delineating  the  skeleton,  the  artist  has  given  to 


Fig.  6. — The  Skeleton,  from  Vesalius's  Fabrica. 


34 


BIOLOGY  AND  ITS  MAKERS 


it  an  artistic  pose,  as  is  shown  in  Fig.  6,  but  nevertheless  the 
bones  are  well  drawn.  No  plates  of  equal  merit  had  ap- 
peared before  these;  in  fact,  they  are  the  earhest  generally 

known  drawings  in  anatomy,  al- 
though woodcuts  representing 
anatomical  figures  were  pub- 
lished as  early  as  149 1  by  John 
Ketham.  Ketham's  figures 
showed  only  externals  and  pre- 
parations for  opening  the  body, 
but  rude  woodcuts  representing 
internal  anatomy  and  the  hu- 
man skeleton  had  been  pub- 
lished notably  by  Magnus 
Hundt,  1 501;  Phrysen,  15 18; 
and  Berengarius,  1521  and 
1523.  Leonardo  da  Vinci  and 
other  artists  had  also  executed 
anatomical  drawings  before  the 
time  of  Vesalius. 

Previous  to  the  publication 
of  the  complete  work,  Vesalius, 
in  1 538,  had  published  six  tables 
of  anatomy,  and,  in  1555,  he 
brought  out  a  new  edition  of  the 
Fabrica,  with  slight  additions, 
especially  in  reference  to  physi- 
ology, which  will  be  adverted  to 
in  the  chapter  on  Harvey. 

In  the  original  edition  of  1543 
the  illustrations  are  not  col- 
lected in  the  form  of  plates,  but 
Fig.  7.— Initial  letters  from       are  distributed  through  the  text, 
Yesalius's  Fabrica  oi  1543.         the  larger  ones  making  full-page 


OVERTHROW  OF  AUTHORITY  IN  SCIENCE  35 

(folio)  illustrations.  In  this  edition  also  the  chapters  are  in- 
troduced with  an  initial  letter  showing  curious  anatomical 
figures  in  miniature,  some  of  which  are  shown  in  Fig.  7. 

The  Fahrica  of  Vesalius  was  a  piece  of  careful,  honest  work, 
the  moral  influence  of  which  must  not  be  overlooked.  At  any 
moment  in  the  world's  history,  work  marked  by  sincerity  ex-v 
ercises  a  wholesome  influence,  but  at  this  particular  stage 
of  intellectual  development  such  work  was  an  innovation,  and 
its  significance  for  progress  was  wider  and  deeper  than  it 
might  have  been  under  different  circumstances. 

Opposition  to  Vesalius. — The  beneficent  results  of  his 
efforts  were  to  unfold  afterward,  since,  at  the  time,  his  utter- 
ances were  vigorously  opposed  from  all  sides.  Not  only  did 
the  ecclesiastics  contend  that  he  was  disseminating  false  and 
harmful  doctrine,  but  the  medical  men  from  whom  he  might 
have  expected  sympathy  and  support  violently  opposed  his 
teachings. 

Many  amusing  arguments  were  brought  forward  to  dis- 
credit VesaKus,  and  to  uphold  the  authority  of  Galen. 
Vesalius  showed  that  in  the  human  body  the  lower  jaw  is 
a  single  bone — that  it  is  not  divided  as  it  is  in  the  dog  and 
other  lower  mammals,  and,  as  Galen  had  taught,  also  in  the 
human  subjects.  He  showed  that  the  sternum,  or  breast 
bone,  has  three  parts  instead  of  eight;  he  showed  that  the 
thigh  bones  are  straight  and  not  cui-yed,  as  they  are  in  the  dog. 
Sylvius,  his  old  teacher,  was  one  of  his  bitterest  opponents; 
he  declared  that  the  human  body  had  undergone  changes  in 
structure  since  the  time  of  Galen,  and,  with  the  object  of  de- 
fending the  ancient  anatomist,  "  he  asserted  that  the  straight 
thigh  bones,  which,  as  every  one  sav/,  were  not  curved  in 
accordance  with  the  teaching  of  Galen,  were  the  result  of 
the  narrow  trousers  of  his  contemporaries,  and  that  they 
must  have  been  curved  in  their  natural  condition,  when  un- 
interfered  with  bv  art!  " 


3^  BIOLOGY   AND    ITS    MAKERS 

The  theologians  also  found  other  points  for  contention. 
It  was  a  widely  accepted  dogma  that  man  should  have  one 
less  rib  on  one  side,  because  from  the  Scriptural  account 
Eve  was  formed  from  one  of  Adam's  ribs.  This,  of  course, 
Vesalius  did  not  find  to  be  the  case.  It  was  also  generally 
believed  at  this  time  that  there  was  in  the  body  an  indestruc- 
tible resurrection-bone  which  formed  the  nucleus  of  the 
resurrection-body.  Vesalius  said  that  he  would  leave  the 
question  of  the  existence  of  such  a  bone  to  be  decided  by  the 
theologians,  as  it  did  not  appear  to  him  to  be  an  anatomical 
question. 

The  Court  Physician. — The  hand  of  the  church  was  heavy 
upon  him,  and  the  hatred  shown  in  attacks  from  various 
quarters  threw  Vesalius  into  a  state  of  despondency  and 
anger.  In  this  frame  of  mind  he  destroyed  manuscripts  upon 
which  he  had  expended  much  labor.  His  disappointment 
in  the  reception  of  his  work  probably  had  much  to  do  in 
deciding  him  to  relinquish  his  professorship  and  accept  the 
post  of  court  physician  to  Charles  V  of  the  United  Kingdoms 
of  Spain  and  Belgium.  After  the  death  of  Charles,  he 
remained  with  Philip  II,  who  succeeded  to  the  throne.  Here 
he  waxed  rich  and  famous,  but  he  was  always  under  sus- 
picion by  the  clerical  powers,  who  from  time  to  time  found 
means  of  discrediting  him.  The  circumstances  of  his  leaving 
Spain  are  not  definitely  known.  One  account  has  it  that  he 
made  a  post-mortem  examination  of  a  body  which  showed 
signs  of  life  during  the  operation,  and  that  he  was  required 
to  undertake  a  pilgrimage  to  the  Holy  Land  to  clear  his  soul 
of  sacrilege.  Whether  or  not  this  was  the  reason  is  uncertain, 
but  after  nineteen  years  at  the  Spanish  Court  he  left,  in  1563, 
and  journeyed  to  Jerusalem.  On  his  return  from  Palestine 
he  suffered  shipwreck  and  died  from  the  effects  of  exposure 
on  Zanti,  one  of  the  Ionian  Islands.  It  is  also  said  that 
while  on  this  pilgrimage  he  had  been  offered  the  position  of 


OVERTHROW    OF    AUTHORITY    IN    SCIENCE        37 

professor  of  anatomy  as  successor  to  Fallopius,  who  had 
died  in  1563,  and  that,  had  he  lived,  he  would  have  come 
back  honorably  to  his  old  post. 

Eustachius  and  Fallopius. — The  work  of  two  of  his  con- 
temporaries, Eustachius  and  Fallopius,  requires  notice. 
Cuvier  says  in  his  Histoire  des  Sciences  Naturelles  that  those 
three  men  were  the  founders  of  modern  anatomy.     Vesalius 


Fig.  8. — Fallopius,  1523-1563. 

was  a  greater  man  than  either  of  the  other  two,  and  his 
influence  was  more  far-reaching.  He  reformed  the  entire 
field  of  anatomy,  while  the  names  of  Eustachius  and  Fallopius 
are  connected  especially  with  a  smaller  part  of  the  field. 
Eustachius  described  the  Eustachian  tube  of  the  ear  and  gave 
especial  attention  to  sense  organs;  Fallopius  made  special 
investigations  upon  the  viscera,  and  described  the  Fallopian 
tube. 


3^  BIOLOGY    AND    ITS    MAKERS 

Fallopius  was  a  suave,  polite  man,  who  became  professor 
of  anatomy  at  Padua;  he  opposed  Vesalius,  but  his  attacks 
were  couched  in  respectful  terms. 

Eustachius,  the  professor  of  anatomy  at  R.ome,  was  of  a 
different  type,  a  harsh,  violent  man,  who  assailed  Vesalius 
with  virulence.  He  corrected  some  mistakes  of  Vesalius, 
and  prepared  new  plates  on  anatomy,  which,  however,  were 
not  published  until  1754,  and  therefore  did  not  exert  the  in- 
fluence upon  anatomical  studies  that  those  of  Vesalius  did. 

The  Especial  Service  of  Vesalius. — It  should  be  remem- 
bered that  both  these  men  had  the  advantage  of  the  sketches 
made  under  the  direction  of  Vesalius.  Pioneers  and  path- 
breakers  are  under  special  limitations  of  being  in  a  new 
territory,  and  make  more  errors  than  they  would  in  following 
another's  survey  of  the  same  territory;  it  takes  much  less 
creative  force  to  correct  the  errors  of  a  first  survey  than 
to  make  the  original  discoveries.  Everything  considered, 
Vesalius  is  deserving  of  the  position  assigned  to  him.  He 
was  great  in  a  larger  sense,  and  it  was  his  researches  in 
particular  which  re-established  scientific  method  and  made 
further  progress  possible.  His  errors  were  corrected,  not  by 
an  appeal  to  authority,  but  by  the  method  which  he  founded. 
His  great  claim  to  renown  is,  not  that  his  work  outshone  all 
other  work  (that  of  Galen  in  particular)  in  accuracy  and 
brilliancy,  but  that  he  overthrew  dependence  on  authority 
and  re-established  the  scientific  method  of  ascertaining  truth. 
It  was  the  method  of  Aristotle  and  Galen  given  anew  to  the 
world. 

The  spirit  of  progress  was  now  released  from  bondage, 
but  we  have  still  a  long  way  to  go  under  its  guidance  to  reach 
the  gateway  of  modern  biology. 


CHAPTER    III 

WILLIAM  HARVEY  AND  EXPERIMENTAL  OBSERVA- 
TION 

After  the  splendid  observations  of  Vesalius,  revealing  in 
a  new  light  the  construction  of  the  human  body.  Harvey  took 
the  next  general  step  by  introducing  experiment  to  determine 
the  use  or  purpose  of  the  structures  that  Vesalius  had  so 
clearly  exposed.  Thus  the  work  of  Harvey  was  complemental 
to  that  of  Vesalius,  and  we  may  safely  say  that,  taken  together, 
the  work  of  these  two  men  laid  the  foundations  of  the  modern 
method  of  investigating  nature.  The  results  they  obtained, 
and  the  influence  of  their  method,  are  of  especial  interest  to  us 
in  the  present  connection,  inasmuch  as  they  stand  at  the 
beginning  of  biological  science  after  the  Renaissance.  Al- 
though the  observations  of  both  were  applied  mainly  to  the 
human  body,  they  served  to  open  the  entire  field  of  structural 
studies  and  of  experimental  observations  on  living  organisms. 

Many  of  the  experiments  of  Harvey,  notably  those  relating 
to  the  movements  of  the  heart,  were,  of  course,  conducted 
upon  the  lower  animals,  as  the  frog,  the  dog,  etc.  His  ex- 
periments on  the  living  human  body  consisted  mainly  in 
applying  ligatures  to  the  arms  and  the  legs.  Nevertheless, 
the  results  of  all  his  experiments  related  to  the  phenomena  of 
the  circulation  in  the  human  body,  and  were  primarily  for 
the  use  of  medical  men. 

In  what  sense  the  observations  of  the  two  men  were  com- 
plemental will  be  better  understood  when  we  remember  that 
there  are  two  aspects  in  which  living  organisms  should 
always  be  considered  in  biological  studies;   first,  the  struc- 

39 


40  BIOLOGY   AND    ITS    MAKERS 

ture,  and,  then,  the  use  that  the  structures  subserve.  One 
view  is  essential  to  the  other,  and  no  investigation  of  animals 
and  plants  is  complete  in  which  the  two  ideas  are  not  in- 
volved. Just  as  a  knowledge  of  the  construction  of  a  ma- 
chine is  necessary  to  understand  its  action,  so  the  anatomical 
analysis  of  an  organ  must  precede  a  knowledge  of  its  office. 
The  term  "  physiological  anatomy  of  an  organ,"  so  commonly 
used  in  text-books  on  physiology,  illustrates  the  point.  We 
can  not  appreciate  the  work  of  such  an  organ  as  the  liver 
without  a  knowledge  of  the  arrangement  of  its  working  units. 
The  work  of  the  anatomist  concerns  the  statics  of  the  body, 
that  of  the  physiologist  the  dynamics;  properly  combined, 
they  give  a  complete  picture  of  the  living  organism. 

It  is  to  be  remembered  that  the  observations  of  Vesalius 
were  not  confined  exclusively  to  structure;  he  made  some 
experiments  and  some  comments  on  the  use  of  parts  of  the 
body,  but  his  work  was  mainly  structural,  while  that  which 
distinguishes  Harvey's  research  is  inductions  founded  on 
experimental  observation  of  the  action  of  living  tissues. 

The  service  of  Vesalius  and  Harvey  in  opening  the  path 
to  biological  advance  is  very  conspicuous,  but  they  were  not 
the  only  pioneers ;  their  work  was  a  part  of  the  general  revival 
of  science  in  which  Galileo,  Descartes,  and  others  had  their 
part.  While  the  birth  of  the  experimental  method  was  not 
due  to  the  exertions  of  Harvey  alone,  nevertheless  it  should 
stand  to  his  credit  that  he  established  that  method  in  bio- 
logical lines.  Aristotle  and  Galen  both  had  employed  ex- 
periments in  their  researches,  and  Harvey's  step  was  in  the 
nature  of  a  revival  of  the  method  of  the  old  Greeks. 

Harvey's  Education. — Harvey  was  fitted  both  by  native 
talent  and  by  his  training  for  the  part  which  he  played  in  the 
intellectual  awakening.  He  was  bom  at  Folkestone,  on  the 
south  coast  of  England,  in  1578,  the  son  of  a  prosperous 
yeoman.     The  Harvey  family  was  well  esteemed,  and  the 


HARVEY  AND  EXPERIMENTAL  OBSERVATION       41 

father  of  William  was  at  one  time  the  mayor  of  Folkestone. 
Young  Harvey,  after  five  years  in  the  King's  school  at  Canter- 
bury, went  to  Cambridge,  and  in  1593,  at  the  age  of  sixteen, 
entered  Caius  College.  He  had  already  shown  a  fondness 
for  observations  upon  the  organization  of  animals,  but  it  is 
unlikely  that  he  was  able  to  cultivate  this  at  the  university. 
There  his  studies  consisted  mainly  of  Latin  and  Greek,  with 
some  training  in  debate  and  elementary  instruction  in  the 
science  of  physics. 

At  Padua. — In  1597,  at  the  age  of  nineteen,  he  was  grad- 
uated with  the  Arts  degree,  and  the  following  year  he  turned 
his  steps  toward  Italy  in  search  of  the  best  medical  instruc- 
tion that  could  be  found  at  that  time  in  all  the  world.  He 
selected  the  great  university  of  Padua  as  his  place  of  sojourn, 
being  attracted  thither  by  the  fame  of  some  of  its  medical 
teachers.  He  was  particularly  fortunate  in  receiving  his 
instruction  in  anatomy  and  physiology  from  Fabricius,  one 
of  the  most  learned  and  highly  honored  teachers  in  Italy. 
The  fame  of  this  master  of  medicine,  who,  from  his  birth- 
place, is  usually  given  the  full  name  of  Fabricius  ah  Aqua- 
pendente,  had  spread  to  the  intellectual  centers  of  the  world, 
where  his  work  as  anatomist  and  surgeon  was  especially 
recognized.  A  fast  friendship  sprang  up  between  the  young 
medical  student  and  this  ripe  anatomist,  the  influence  of  which 
must  have  been  very  great  in  shaping  the  future  work  of  Harvey. 

Fabricius  was  already  sixty-one  years  of  age,  and  when 
Harvey  came  to  Padua  was  perfecting  his  knowledge  upon 
the  valves  of  the  veins.  The  young  student  was  taken  fully 
into  his  confidence,  and  here  was  laid  that  first  familiarity 
with  the  circulatory  system,  the  knowledge  of  which  Harvey 
was  destined  so  much  to  advance  and  amplify.  But  it  was 
the  stimulus  of  his  master's  friendship,  rather  than  what  he 
taught  about  the  circulation,  that  was  of  assistance  to  Harvey. 
For  the  views  of  Fabricius  in  reference  to  the  circulation  were 


42  BIOLOGY   AND    ITS    MAKERS 

those  of  Galen;  and  his  conception  of  the  use  of  the  valves 
of  the  veins  was  entirely  wrong.  A  portrait  of  this  great 
teacher  of  Harvey  is  shown  in  Fig.  9. 

At  Padua  young  Harvey  attracted  notice  as  a  student  of 
originality  and  force,  and  seems  to  have  been  a  favorite  with 
the  student  body  as  well  as  with  his  teachers.  His  position 
in  the  university  may  be  inferred  from  the  fact  that  he  be- 
longed to  one  of  the  aristocratic-student  organizations,  and, 
further,  that  he  was  designated  a  "  councilor"  for  England. 
The  practice  of  havdng  student  councilors  was  then  in  vogue 
in  Padua;  the  students  comprising  the  council  met  for 
deliberations,  and  very  largely  managed  the  university  by 
their  votes  upon  instructors  and  university  measures. 

It  is  a  favorable  comment  upon  the  professional  education 
of  his  time  that,  after  graduating  at  the  University  of  Cam- 
bridge, he  studied  four  or  more  years  (Willis  says  five  years) 
in  scientific  and  medical  lines  to  reach  the  degree  of  Doctor 
of  Physic. 

On  leaving  Padua,  in  1602,  he  returned  to  England  and 
took  the  examinations  for  the  degree  of  M.D.  from  Cam- 
bridge, inasmuch  as  the  medical  degree  from  an  English 
university  advanced  his  prospects  of  receiving  a  position  at 
home.  He  opened  practice,  was  married  in  1604,  and  the 
same  year  began  to  give  public  lectures  on  anatomy. 

His  Personal  Qualities. — Harvey  had  marked  individual- 
ity, and  seems  to  have  produced  a  powerful  impression  upon 
those  with  whom  he  came  in  contact  as  one  possessing 
unusual  intellectual  powers  and  independence  of  character. 
He  inspired  confidence  in  people,  and  it  is  significant  that, 
in  reference  to  the  circulation  of  the  blood,  he  won  to  his  way 
of  thinking  his  associates  in  the  medical  profession.  This  is 
important  testimony  as  to  his  personal  force,  since  his  ideas 
were  opposed  to  the  belief  of  the  time,  and  since  also  away 
from  home  they  were  vigorously  assailed. 


Fig.  9. — Fabricius,   1537-1619,  Harvey's  Teacher. 


44 


BIOLOGY   AND    ITS    MAKERS 


Although  described  as  choleric  and  hasty,  he  had  also 
winning  qualities,  so  that  he  retained  warm  friendships 
throughout  his  life,  and  was  at  all  times  held  in  high  respect. 


Fig.   io. — William  Harvey,   1578-1667. 


It  must  be  said  also  that  in  his  replies  to  his  critics,  he  showed 
great  moderation. 

The  contemplative  face  of  Harvey  is  shown  in  Fig.  10. 
This  is  taken  from  his  picture  in  the  National  Portrait 
Gallery  in  London,  and  is  usually  regarded  as  the  second- 


HARVEY  AND  EXPERIMENTAL  OBSERVATION       45 

best  portrait  of  Harvey,  since  the  one  painted  by  Jansen, 
now  in  possession  of  the  Royal  College  of  Physicians,  is 
believed  to  be  the  best  one  extant.  The  picture  reproduced 
here  shows  a  countenance  of  composed  intellectual  strength, 
with  a  suggestion,  in  the  forehead  and  outline  of  the  face,  of 
some  of  the  portraits  of  Shakespeare. 

x\n  idea  of  his  personal  appearance  may  be  had  from  the 
description  of  Aubrey,  who  says :  ''  Harvey  was  not  tall,  but  of 
the  lowest  stature;  round  faced,  with  a  complexion  like  the 
wainscot ;  his  eyes  small,  round,  very  black,  and  full  of  spirit ; 
his  hair  black  as  a  raven,  but  quite  white  twenty  years  before 
he  died;  rapid  in  his  utterance,  choleric,  given  to  gesture," 
etc. 

He  was  less  impetuous  than  Vesalius,  who  had  published 
his  work  at  twenty-eight;  Harvey  had  demonstrated  his  ideas 
of  the  circulation  in  public  anatomies  and  lectures  for  twelve 
years  before  publishing  them,  and  when  his  great  classic  on 
the  Movement  of  the  Heart  and  Blood  first  appeared  in  1628, 
he  was  already  fifty  years  of  age.  This  is  a  good  example  for 
young  investigators  of  to-day  who,  in  order  to  secure  priority 
of  announcement,  so  frequently  rush  into  print  wnth  imperfect 
observations  as  preliminary  communications. 

Harvey's  Writings. — Harvey's  publications  were  all  great ; 
in  embryology,  as  in  physiology,  he  produced  a  memorable 
treatise.  But  his  publications  do  not  fully  represent  his 
activity  as  an  investigator;  it  is  known  that  through  the 
fortunes  of  war,  while  connected  with  the  sovereign  Charles  I. 
as  court  physician,  he  lost  manuscripts  and  drawings  upon 
the  comparative  anatomy  and  development  of  insects  and 
other  animals.  His  position  in  embryology  will  be  dealt 
w^ith  in  the  chapter  on  the  Development  of  Animals,  and  he 
will  come  up  for  consideration  again  in  the  chapter  on  the 
Rise  of  Physiology.  Here  we  are  concerned  chiefly  with  his 
general  influence  on  the  development  of  biology. 


46  BIOLOGY   AND    ITS    MAKERS 

His  Great  Classic  on  Movement  of  the  Heart  and  Blood. 

— Since  his  book  on  the  circulation  of  the  blood  is  regarded 
as  one  of  the  greatest  monuments  along  the  highroad  of  biol- 
og)%  it  is  time  to  make  mention  of  it  in  particular.  Although 
relatively  small,  it  has  a  long  title  out  of  proportion  to  its 
size:  Exercitatio  Anatomica  de  Motu  Cordis  et  Sanguinis  in 
Animalibus,  which  maybe  freely  translated,  '^  An  Anatomical 
Disquisition  on  the  Movement  of  the  Heart  and  Blood  in 
Animals."  The  book  is  usually  spoken  of  under  the  shorter 
title,  De  Motu  Cordis  et  Sanguinis.  The  full  title  seems  some- 
what repellent,  but  the  contents  of  the  book  will  prove  to  be 
interesting  to  general  readers.  It  is  a  clear,  logical  demon- 
stration of  the  subject,  proceeding  with  directness  from  one 
point  to  another  until  the  culminating  force  of  the  argument 
grows  complete  and  convincing. 

The  book  in  its  first  edition  was  a  quarto  volume  of 
seventy-eight  pages,  published  in  Frankfort  in  1628.  An 
interesting  facsimile  reprint  of  this  work,  translated  into 
English,  was  privately  reproduced  in  1894  by  Dr.  Moreton 
and  published  in  Canterbury.  As  stated  above,  it  is  known 
that  Harvey  had  presented  and  demonstrated  his  views  in 
his  lectures  since  161 6.  In  his  book  he  showed  for  the  first 
time  ever  in  print,  that  all  the  blood  in  the  body  moves  in  a 
circuit,  and  that  the  beating  of  the  heart  supplies  the  propel- 
ling force.  Both  ideas  were  new,  and  in  order  to  appreciate 
in  what  sense  they  were  original  with  Harvey,  we  must 
inquire  into  the  views  of  his  forerunners. 

Question  as  to  Harvey's  Originality. — The  question  of 
how  near  some  of  his  predecessors  came  to  anticipating  his 
demonstration  of  the  circulation  has  been  much  debated. 
It  has  been  often  maintained  that  Servetus  and  Realdus 
Columbus  held  the  conception  of  the  circulation  for  which 
Harvey  has  become  so  celebrated.  Of  the  various  accounts 
of  the  views  of  Harvey's  predecessors,  those  of  Willis,  Huxley, 


HARVEY  AND  EXPERIMENTAL  OBSERVATION       47 

and  Michael  Foster  are  among  the  most  judicial;  that  of 
Foster,  indeed,  inasmuch  as  it  contains  ample  quotations 
from  the  original  sources,  is  the  most  nearly  complete  and 
satisfactory.  The  discussion  is  too  long  to  enter  into  fully 
here,  but  a  brief  outline  is  necessary  to  understand  what 
he  accomplished,  and  to  put  his  discovery  in  the  proper 
light. 

To  say  that  he  first  discovered — or,  more  properly, 
demonstrated—the  circulation  of  the  blood  carries  the  im- 
pression that  he  knew  of  the  existence  of  capillaries  connect- 
ing the  arteries  and  the  veins,  and  had  ocular  proof  of  the 
circulation  through  these  connecting  vessels.  But  he  did  not 
actually  see  the  blood  moving  from  veins  to  arteries,  and  he 
knew  not  of  the  capillaries.  He  understood  clearly  from  his 
observations  and  experiments  that  all  the  blood  passes  from 
veins  to  arteries  and  moves  in  "a  kind  of  circle";  still,  he 
thought  that  it  filters  through  the  tissues  in  getting  from  one 
kind  of  vessel  to  the  other.  It  was  reserved  for  Malpighi, 
in  1 66 1,  and  Leeuwenhoek,  in  1669,  to  see,  with  the  aid  of 
lenses,  the  movement  of  the  blood  through  the  capillaries 
in  the  transparent  parts  of  animal  tissues.  (See  under 
Leeuwenhoek,  p.  84.) 

The  demonstration  by  Harvey  of  the  movement  of  the 
blood  in  a  circuit  was  a  matter  of  cogent  reasoning,  based  on 
experiments  with  ligatures,  on  the  exposure  of  the  heart  in 
animals  and  the  analysis  of  its  movements.  It  has  been  com- 
monly maintained  (as  by  Whewell)  that  he  deduced  the  cir- 
culation from  observations  of  the  valves  in  the  veins,  but  this 
is  not  at  all  the  case.  The  central  point  of  Harvey's  reason- 
ing is  that  the  quantity  of  blood  which  leaves  the  left  cavity 
of  the  heart  in  a  given  space  of  time  makes  necessary  its 
return  to  the  heart,  since  in  a  half-hour  (or  less)  the  heart, 
by  successive  pulsations,  throws  into  the  great  artery  more 
than  the  total  quantity  of  blood  in  the  body.     Huxley  points 


48  BIOLOGY   AND    ITS    MAKERS 

out  that  this  is  the  first  time  that  quantitative  determinations 
were  introduced  into  physiology. 

Views  of  His  Predecessors  on  the  Movement  of  the  Blood. 

■ — Galen's  view  of  the  movement  of  the  blood  was  not  com- 
pletely replaced  until  the  establishment  of  Harvey's  view. 
The  Greek  anatomist  thought  that  there  was  an  ebb  and  flow 
of  blood  within  both  veins  and  arteries  throughout  the 
system.  The  left  side  of  the  heart  was  supposed  to  contain 
blood  vitalized  by  a  mixture  of  animal  spirits  within  the  lungs. 
The  veins  were  thought  to  contain  crude  blood.  He  sup- 
posed, further,  that  there  was  a  communication  between  the 
right  and  the  left  side  of  the  heart  through  ver}^  minute  pores 
in  the  septum,  and  that  some  blood  from  the  right  side  passed 
through  the  pores  into  the  left  side  and  there  became  charged 
with  animal  spirits.  It  should  also  be  pointed  out  that  Galen 
believed  in  the  transference  of  some  blood  through  the  lungs 
from  the  right  to  the  left  side  of  the  heart,  and  in  this  fore- 
shadowed the  views  which  were  later  developed  by  Servetus 
and  Realdus  Columbus. 

Vesalius,  in  the  first  edition  of  his  work  (1543)  expressed 
doubts  upon  the  existence  of  pores  in  the  partition-wall  of 
the  heart  through  which  blood  could  pass ;  and  in  the  second 
edition  (1555)  of  the  Fabrica  he  became  more  skeptical. 
In  taking  this  position  he  attacked  a  fundamental  part  of 
the  belief  of  Galen.  The  careful  structural  studies  of  Vesalius 
must  have  led  him  very  near  to  an  understanding  of  the  con- 
nection between  arteries  and  veins.  Fig.  11  shows  one  of 
his  sketches  of  the  arrangement  of  arteries  and  veins.  He 
saw  that  the  minute  terminals  of  arteries  and  veins  came  very 
close  together  in  the  tissues  of  the  body,  but  he  did  not  grasp 
the  meaning  of  the  observation,  because  his  physiology  was 
still  that  of  Galen;  Vesalius  continued  to  believe  that  the 
arteries  contained  blood  mixed  with  spirits,  and  the  veins 
crude  blood,  and  his  idea  of  the  movement  was  that  of  an 


HARVEY  AND  EXPERIMENTAL  OBSERVATION       49 

ebb  and  flow.  In  reference  to  the  anatomy  of  the  blood- 
vessels, he  goes  so  far  as  to  say  of  the  portal  vein  and  the 
vena  cava  in  the  liver  that  "  the  extreme  ramifications  of  these 
vems  inosculate  with  each  other,  and  in  many  places  appear 


Fig. 


-Scheme  of  the  Portal  Circulation  According 
to  Vesalius,   1543. 


to  unite  and  be  continuous."  All  who  followed  him  had  the 
advantage  of  his  drawings  showing  the  parallel  arrangement 
of  arteries  and  veins,  and  their  close  approach  to  each  other 
in  their  minute  terminal  twigs,  but  no  one  before  Harvey 


50  BIOLOGY   AND    ITS    MAKERS 

fully  grasped  the  idea  of  the  movement  of  the  blood  in  a 
complete  circuit. 

Servetus,  in  his  work  on  the  Restoration  of  Christianity 
{Restitutio  Christianismi,  i553))  the  work  for  which  Calvin 
accomplished  his  burning  at  the  stake,  expressed  more 
clearly  than  Galen  had  done  the  idea  of  a  circuit  of  blood 
through  the  lungs.  According  to  his  view,  some  of  the  blood 
took  this  course,  while  he  still  admits  that  a  part  may  exude 
through  the  wall  of  the  ventricle  from  the  right  to  the  left 
side.  This,  however,  was  embodied  in  a  theological  treatise, 
and  had  little  direct  influence  in  bringing  about  an  altered 
view  of  the  circulation.  Nevertheless,  there  is  some  reason 
to  think  that  it  may  have  been  the  original  source  of  the  ideas 
of  the  anatomist  Columbus,  as  the  studies  into  the  character 
of  that  observer  by  Michael  Foster  seem  to  indicate. 

Realdus  Columbus,  professor  of  anatomy  at  Rome,  ex- 
pressed a  conception  almost  identical  with  that  of  Servetus, 
and  as  this  was  in  an  important  work  on  anatomy,  published 
in  1559,  and  well  known  to  the  medical  men  of  the  period, 
it  lay  in  the  direct  line  of  anatomical  thought  and  had  greater 
influence.  Foster  suggests  that  the  devious  methods  of 
Columbus,  and  his  unblushing  theft  of  intellectual  property 
from  other  sources,  give  ground  for  the  suspicion  that  he  had 
appropriated  this  idea  from  Servetus  without  acknowledg- 
ment. Although  Calvin  supposed  that  the  complete  edition 
of  a  thousand  copies  of  the  work  of  Servetus  had  been  burned 
with  its  author  in  1553,  a  few  copies  escaped,  and  possibly 
one  of  these  had  been  examined  by  Columbus.  This  as- 
sumption is  strengthened  by  the  circumstance  that  Columbus 
gives  no  record  of  observations,  but  almost  exactly  repeats 
the  words  of  Servetus. 

Caesalpinus,  the  botanist  and  medical  man,  expressed  in 
1 571  and  1593  similar  ideas  of  the  movement  of  the  blood 
(probably  as  a  matter  of  argument,  since  there  is  no  record 


HARVEY  AND  EXPERIMENTAL  OBSERVATION       5^ 

of  either  observations  or  experiments  by  him).  He  also  laid 
hold  of  a  still  more  important  conception,  viz.,  that  some  of 
the  blood  passes  from  the  left  side  of  the  heart  through  the 
arteries  of  the  body,  and  returns  to  the  right  side  of  the  heart 
by  the  veins.  But  a  fair  consideration  of  the  claims  of  these 
men  as  forerunners  of  Harvey  requires  quotations  from  their 
works  and  a  critical  examination  of  the  evidence  thus  adduced. 
This  has  been  excellently  done  by  Michael  Foster  in  his  Lec- 
tures on  the  History  of  Physiology.  Further  considerations 
of  this  aspect  of  the  question  would  lie  beyond  the  purposes 
of  this  book. 

At  most,  before  Harvey,  the  circuit  through  the  lungs  had 
been  vaguely  divined  by  Galen,  Servetus,  Columbus,  and 
Caesalpinus,  and  the  latter  had  supposed  some  blood  to  pass 
from  the  heart  by  the  arteries  and  to  return  to  it  by  the  veins; 
but  no  one  had  arrived  at  an  idea  of  a  complete  circulation 
of  all  the  blood  through  the  system,  and  no  one  had  grasped 
the  consequences  involved  in  such  a  conception.  Harvey's 
idea  of  the  movement  of  the  heart  (De  Motu  Cordis)  was  new; 
his  notion  of  the  circulation  {et  Sanguinis)  was  new;  and 
his  method  of  demonstrating  these  was  new. 

Harvey's  Argument. — The  gist  of  Harvey's  arguments  is 
indicated  in  the  following  propositions  quoted  with  slight 
modifications  from  Hall's  Physiology:  (I)  The  heart  pas- 
sively dilates  and  actively  contracts ;  (II)  the  auricles  contract 
before  the  ventricles  do;  (III)  the  contraction  of  the  auricles 
forces:,  the  blood  into  the  ventricles;  (IV)  the  arteries  have 
no  ^'pulsific  power,"  i.e.,  they  dilate  passively,  since  the  pul- 
sation of  the  arteries  is  nothing  else  than  the  impulse  of  the 
blood  within  them ;  (V)  the  heart  is  the  organ  of  propulsion 
of  the  blood ;  (VI)  in  passing  from  the  right  ventricle  to  the 
left  auricle  the  blood  transudes  through  the  parenchyma  of 
the  lungs ;  (VII)  the  quantity  and  rate  of  passage  of  the  blood 
peripherally  from  the  heart  makes  it  a  physical  necessity  that 


52  BIOLOGY   AND    ITS    MAKERS 

most  of  the  blood  return  to  the  heart ;  (VIII)  the  blood  does 
return  to  the  heart  by  way  of  the  veins.  It  will  be  noticed 
that  the  proposition  VII  is  the  important  one;  in  it  is 
involved  the  idea  of  applying  measurement  to  a  physiological 
process. 

Harvey's  Influence. — Harvey  was  a  versatile  student. 
He  was  a  comparative  anatomist  as  well  as  a  physiologist 
and  embryologist ;  he  had  investigated  the  anatomy  of  about 
sixty  animals  and  the  embryology  of  insects  as  well  as  of 
vertebrates,  and  his  general  influence  in  promoting  biological 
work  was  extensive. 

His  work  on  the  movement  of  the  blood  was  more  than 
a  record  of  a  series  of  careful  investigations;  it  was  a  land- 
mark in  progress.  When  we  reflect  on  the  part  played  in 
the  body  by  the  blood,  we  readily  see  that  a  correct  idea  of 
how  it  carries  nourishment  to  the  tissues,  and  how  it  brings 
away  from  them  the  products  of  disintegrated  protoplasm  is 
of  prime  importance  in  physiology.  It  is  the  point  from 
which  spring  all  other  ideas  of  the  action  of  tissues,  and  until 
this  was  known  the  fine  analysis  of  vital  processes  could  not 
be  made.  The  true  idea  of  respiration,  of  the  secretion  by 
glands,  the  chemical  changes  in  the  tissues,  in  fact,  of  all  the 
general  activities  of  the  body,  hinge  upon  this  conception. 
It  was  these  consequences  of  his  demonstration,  rather  than 
the  fact  that  the  blood  moves  in  a  circuit,  which  made  it  so 
important.  This  discovery  created  modem  physiology,  and 
as  that  branch  of  inquiry  is  one  of  the  parts  of  general  biology, 
the  bearing  of  Harvey's  discovery  upon  biological  thought 
can  be  readily  surmised. 

Those  who  wish  to  examine  Harvey's  views  at  first  hand, 
without  the  burden  of  translating  them  from  the  Latin,  will 
find  an  edition  of  his  complete  works  translated  into  English 
by  Willis,  and  published  by  the  Ray  Society,  of  London. 

As  is  always  the  case  with  new  truths,  there  was  hostility 


HARVEY  AND  EXPERIMENTAL  OBSERVATION       53 

to  accepting  his  views.  In  England  this  hostility  was  slight 
on  account  of  his  great  personal  influence,  but  on  the  Conti- 
nent there  was  many  a  sharp  criticism  passed  upon  his  work. 
His  views  were  so  illuminating  that  they  were  certain  of 
triumph,  and  even  in  his  lifetime  were  generally  accepted. 
Thus  the  new  conception  of  vital  activities,  together  with  his 
method  of  inquiry,  became  permanent  parts  of  biological 
science. 


CHAPTER  IV 

THE    INTRODUCTION    OF   THE    MICROSCOPE   AND 
THE  PROGRESS  OF  INDEPENDENT  OBSERVATION 

The  introduction  of  the  microscope  greatly  increased  the 
ocular  powers  of  observers,  and,  in  the  seventeenth  century, 
led  to  many  new  departures.  By  its  use  the  observations 
were  carried  from  the  plane  of  gross  anatomy  to  that  of 
minute  structure;  the  anatomy  of  small  forms  of  life,  like  in- 
sects, began  to  be  studied,  and  also  the  smaller  microscopic 
animalcula  were  for  the  first  time  made  known. 

Putting  aside  the  disputed  questions  as  to  the  time  of  the 
invention  and  the  identity  of  the  inventor  of  the  microscope — 
whether  to  Fontana,  Galileo,  or  the  Jenssens  belongs  the 
credit — we  know  that  it  was  improved  by  the  Hollander 
Drebbel  in  the  early  years  of  the  seventeenth  century,  but 
was  not  seriously  applied  to  anatomical  studies  till  after  the 
middle  of  that  century. 

« 
The  Pioneer  Microscopists 

The  names  especially  associated  with  early  microscopic 
observations  are  those  of  Hooke  and  Grew  in  England, 
Malpighi  in  Italy,  and  Swammerdam  and  Leeuwenhoek, 
both  in  Holland.  Their  microscopes  were  imperfect,  and 
were  of  two  kinds :  simple  lenses,  and  lenses  in  combination, 
forming  what  we  now  know  as  the  compound  microscope. 
Some  forms  of  these  early  microscopes  will  be  described  and 
illustrated  later.     Although  thus   early  introduced,   micro- 

54 


INTRODUCTION    OF   THE    MICROSCOPE 


55 


scopic  observation  did  not  produce  its  great  results  until  the 
nineteenth  century,  just  after  magnifying-lenses  had  been 
greatly  improved. 

Robert  Hooke  (1635-1703),  of  London,  published  in  1665 
a  book  of  observations  with  the  microscope  entitled  Micro- 
graphia,  which  was  embellished  with  eighty- three  plates  of 
figures.  Hooke  was  a  man  of  fine  mental  endowment,  who 
had  received  a  good  scientific 
training  at  the  University  of 
Cambridge,  but  who  lacked 
fixedness  of  purpose  in  the 
employment  of  his  talents. 
He  did  good  work  in  math- 
ematics, made  many  models 
for  experimenting  with  flying 
machines,  and  claimed  to  have 
discovered    gravitation    before 


Fig.   12. — Hooke's  Microscope,   1665. 

From  Carpenter's  T/ie  Microscope  and  Its  Revelations.     Permission  of 
P.  Blakiston's  Sons  &  Co. 


56  BIOLOGY   AND    ITS    MAKERS 

Newton,  and  also  the  use  of  a  spring  for  regulating  watches 
before  Huygens,  etc.  He  gave  his  attention  to  microscopic 
study  for  a  time  and  then  dropped  it ;  yet,  although  we  can  not 
accord  to  him  a  prominent  place  in  the  history  of  biology, 
he  must  receive  mention  as  a  pioneer  worker  with  the  micro- 
scope. His  book  gave  a  powerful  stimulus  to  microscopy  in 
England,  and,  partly  through  its  influence,  labor  in  this  field 
was  carried  on  more  systematically  by  his  fellow-countryman 
Nehemiah  Grew. 

The  form  of  the  microscope  used  by  Hooke  is  known 
through  a  picture  and  a  description  which  he  gives  of  it 
in  his  Micro graphia.  Fig.  1 2  is  a  copy  of  the  illustration. 
His  was  a  compound  microscope  consisting  of  a  combination 
of  lenses  attached  to  a  tube,  one  set  near  the  eye  of  the  ob- 
server and  the  other  near  the  object  to  be  examined.  When 
we  come  to  describe  the  microscopes  of  Leeuwenhoek,  with 
which  so  much  good  work  was  accomplished,  we  shall  see 
that  they  stand  in  marked  contrast,  on  account  of  their  sim- 
plicity, to  the  somewhat  elaborate  instrument  of  Hooke. 

Grew  (1628-1711)  devoted  long  and  continuous  labor  to 
microscopic  observation,  and,  although  he  was  less  versatile 
and  brilliant  than  Hooke,  his  patient  investigations  give  him 
just  claim  to  a  higher  place  in  the  history  of  natural  science. 
Grew  applied  the  microscope  especially  to  the  structure  of 
plants,  and  his  books  entitled  Idea  oj  a  Philosophical  His- 
tory of  Plants  (1673)  and  Anatomy  of  Vegetables  (1682) 
helped  to  lay  the  foundations  of  vegetable  histology.  When 
we  come  to  consider  the  work  of  Malpighi,  we  shall  see  that 
he  also  produced  a  work  upon  the  microscopic  structure  of 
plants  which,  although  not  more  exact  and  painstaking  than 
Grew's,  showed  deeper  comprehension.  He  is  the  co- 
founder  with  Grew  of  the  science  of  the  microscopic  anatomy 
of  plants. 

It  IS  not  necessary  to  dwell  long  upon  the  work  of  either 


INTRODUCTION    OF   THE    MICROSCOPE  57 

Hooke  or  Grew,  since  that  of  Malpighi,  Swammerdam,  and 
Leeuwenhoek  was  more  far-reaching  in  its  influence.  The 
publications  of  these  three  men  were  so  important,  both  in 
reference  to  microscopic  study  and  to  the  progress  of  inde- 
pendent investigation,  that  it  will  be  necessary  to  deal  with 
them  in  more  detail.  In  the  work  of  these  men  we  come 
upon  the  first  fruits  of  the  application  of  the  methods  intro- 
duced by  Vesalius  and  Harvey.  Of  this  triumvirate,  one — 
Malpighi — was  an  Italian,  and  the  other  two  were  Holland- 
ers. Their  great  service  to  intellectual  progress  consisted 
chiefly  in  this — that,  following  upon  the  foundations  of 
Vesalius  and  Harvey,  "  they  broke  away  from  the  thraldom 
of  mere  book-learning,  and  relying  alone  upon  their  own 
eyes  and  their  own  judgment,  won  for  man  that  which  had 
been  quite  lost — the  blessings  of  independent  and  unbiased 
observation." 

It  is  natural  that,  working  when  they  did,  and  independ- 
ently as  they  did,  their  work  overlapped  in  many  ways. 
Malpighi  is  noteworthy  for  many  discoveries  in  anatomical 
science,  for  his  monograph  on  the  anatomy  of  the  silkworm, 
for  observations  of  the  minute  structure  of  plants,  and  of  the 
development  of  the  chick  in  the  hen's  egg.  Swammerdam 
did  excellent  and  accurate  work  upon  the  anatomy  and 
metamorphosis  of  insects,  and  the  internal  structure  of  mol- 
lusks,  frogs,  and  other  animals.  Leeuwenhoek  is  distin- 
guished for  much  general  microscopic  work;  he  discovered 
various  microscopic  animalcula;  he  established,  by  direct 
observation,  the  fact  of  a  connection  between  arteries  and 
veins,  and  examined  microscopically  minerals,  plants,  and 
animals.  To  him,  more  than  to  the  others,  the  general  title 
of  "  microscopist  "  might  be  applied. 

Since  these  men  are  so  important  in  the  growth  of  biol- 
ogy, let  us,  by  taking  them  individually,  look  a  Httle  more 
closely  into  their  Hves  and  labors. 


58  BIOLOGY   AND    ITS    MAKERS 

Marcello  Malpighi,  1628-1694 

Personal  Qualities. — There  are  several  portraits  of  Mal- 
pighi extant.  These,  together  with  the  account  of  his 
personal  appearance  given  by  Atti,  one  of  his  biographers, 
enable  us  to  tell  what  manner  of  man  he  was.  The  portrait 
shown  in  Fig.  13  is  a  copy  of  the  one  painted  by  Tabor  and 
presented  by  Malpighi  to  the  Royal  Society  of  London,  in 
whose  rooms  it  may  still  be  seen.  This  shows  him  in  the 
full  attractiveness  of  his  early  manhood,  with  the  earnest, 
intellectual  look  of  a  man  of  high  ideals  and  scholarly  tastes, 
sweet-tempered,  and  endowed  with  the  insight  that  belongs 
to  a  sympathetic  nature.  Some  of  his  portraits  taken  later 
are  less  attractive,  and  the  lines  and  wrinkles  that  show 
in  his  face  give  evidence  of  imperfect  health.  According  to 
Atti,  he  was  of  medium  stature,  with  a  brown  skin,  a  delicate 
complexion,  a  serious  countenance,  and  a  melancholy  look. 

Accounts  of  his  life  show  that  he  was  modest,  quiet,  and 
of  a  pacific  disposition,  notwithstanding  the  fact  that  he  lived 
in  an  atmosphere  of  acrimonious  criticism,  of  jealousy  and 
controversy.  A  family  dispute  in  reference  to  the  boundary- 
lines  between  his  father's  property  and  the  adjoining  land  of 
the  Sbaraglia  family  gave  rise  to  a  feud,  in  which  representa- 
tives of  the  latter  family  followed  him  all  his  Kf e  with  efforts 
to  injure  both  his  scientific  reputation  and  his  good  name. 
Under  all  this  he  suffered  acutely,  and  his  removal  from 
Bologna  to  Messina  was  partly  to  escape  the  harshness  of 
his  critics.  Some  of  his  best  qualities  showed  under  these 
persecutions;  he  was  dignified  under  abuse  and  considerate 
in  his  reply.  In  reference  to  the  attacks  upon  his  scientific 
standing,  there  were  published  after  his  death  replies  to  his 
critics  that  were  written  while  he  was  smarting  under  their 
injustice  and  severity,  but  these  replies  are  free  from  bitterness 
and  are  written  in  a  spirit  of  great  moderation.     The  follow- 


Fig.   13. — Malpighi,  1628-1694. 


6o  BIOLOGY    AND    ITS    MAKERS 

ing  picture,  taken  from  Ray's  correspondence,  shows  the  fine 
control  of  his  spirit.  Under  the  date  of  April,  1684,  Dr. 
Tancred  Robinson  writes :  "  Just  as  I  left  Bononia  I  had  a 
lamentable  spectacle  of  Malpighi's  house  all  in  flames, 
occasioned  by  the  negligence  of  his  old  wife.  All  his  pic- 
tures, furniture,  books,  and  manuscripts  were  burnt.  I  saw 
him  in  the  very  heat  of  the  calamity,  and  methought  I  never 
beheld  so  much  Christian  patience  and  philosophy  in  any 
man  before;  for  he  comforted  his  wife  and  condoled  nothing 
but  the  loss  of  his  papers." 

Education. — Malpighi  was  born  at  Crevalcuore,  near 
Bologna,  in  1628.  His  parents  were  landed  peasants,  or 
farmers,  enjoying  an  independence  in  financial  matters.  As 
their  resources  permitted  it,  they  designed  to  give  Marcellus, 
their  eldest  child,  the  advantage  of  masters  and  schools. 
He  began  a  life  of  study;  and,  before  long,  he  showed  a  taste 
for  belles-lettres  and  for  philosophy,  which  he  studied  under 
Natali. 

Through  the  death  of  both  parents,  in  1649,  Malpighi 
found  himself  orphaned  at  the  age  of  twenty-one,  and  as  he 
was  the  eldest  of  eight  children,  the  management  of  domestic 
affairs  devolved  upon  him.  He  had  as  yet  made  no  choice 
of  a  profession ;  but,  through  the  advice  of  Natali,  he  resolved, 
in  165 1,  to  study  medicine.  This  advice  followed,  in  1653, 
at  the  age  of  twenty-five,  he  received  from  the  University  of 
Bologna  the  degree  of  Doctor  of  Medicine. 

University  Positions. — In  the  course  of  a  few  years  he 
married  the  sister  of  Massari,  one  of  his  teachers  in  anatomy, 
and  became  a  candidate  for  a  chair  in  the  University  of 
Bologna.  This  he  did  not  immediately  receive,  but,  about 
1656,  he  was  appointed  to  a  post  in  the  university,  and  began 
his  career  as  a  teacher  and  investigator.  He  must  have 
shown  aptitude  for  this  work,  for  he  was  soon  called  to  the 
University  of  Pisa,  where,  fortunately  for  his  development, 


INTRODUCTION    OF    THE    MICROSCOPE  6l 

he  became  associated  with  BoreUi,  who,  as  an  older  man, 
assisted  him  in  many  ways.  They  united  in  some  work,  and 
together  they  discovered  the  spiral  character  of  the  heart 
muscles.  But  the  climate  of  Pisa  did  not  agree  with  him, 
and  after  three  years  he  returned,  in  1659,  to  teach  in  the 
University  of  Bologna,  and  applied  himself  assiduously  to 
anatomy. 

Here  his  fame  was  in  the  ascendant,  notwithstanding  the 
machinations  of  his  enemies  and  detractors,  led  by  Sbaraglia. 
He  was  soon  (1662)  called  to  Messina  to  follow  the  famous 
Castelli.  After  a  residence  there  of  four  years  he  again 
returned  to  Bologna,  and  as  he  was  now  thirty-eight  years 
of  age,  he  thought  it  time  to  retire  to  his  villa  near  the  city 
in  order  to  devote  himself  more  fully  to  anatomical  studies, 
but  he  continued  his  lectures  in  the  university,  and  also  his 
practice  of  medicine. 

Honors  at  Home  and  Abroad. — Malpighi's  talents  were 
appreciated  even  at  home.  The  University  of  Bologna  hon- 
ored him  in  1686  with  a  Latin  eulogium;  the  city  erected  a 
monument  to  his  memory;  and  after  his  death,  in  the  city  of 
Rome,  his  body  was  brought  to  Bologna  and  interred  with 
great  pomp  and  ceremony.  At  the  three  hundredth  anniver- 
sary of  his  death,  in  1894,  a  festival  was  held  in  Bologna, 
his  monument  was  unveiled,  and  a  book  of  addresses  by 
eminent  anatomists  was  published  in  his  honor. 

During  his  lifetime  he  received  recognition  also  from 
abroad,  but  that  is  less  remarkable.  In  1668  he  was  elected 
an  honorary  member  of  the  Royal  Society  of  London.  He 
was  very  sensible  of  this  honor;  he  kept  in  communication 
with  the  society;  he  presented  them  with  his  portrait,  and 
deposited  in  their  archives  the  original  drawings  illustrating 
the  anatomy  of  the  silkworm  and  the  development  of  the  chick. 

In  1 691  he  was  taken  to  Rome  by  the  newly  elected  pope, 
Innocent  XII,  as  his  personal  physician,  but  under  these  new 


62  BIOLOGY   AND    ITS    MAKERS 

conditions  he  was  not  destined  to  live  many  years.  He  died 
there,  in  1694,  of  apoplexy.  His  wife,  of  whom  it  appears 
that  he  was  very  fond,  had  died  a  short  time  previously. 
Among  his  posthumous  works  is  a  sort  of  personal  psychology 
written  down  to  the  year  1691,  in  which  he  shows  the  growth 
of  his  mind,  and  the  way  in  which  he  came  to  take  up  the 
different  subjects  of  investigation. 

In  reference  to  his  discoveries  and  the  position  he  occupies 
in  the  history  of  natural  science,  it  should  be  observed  that 
he  was  an  "  original  as  well  as  a  very  profound  observer." 
While  the  ideas  of  anatomy  were  still  vague,  "  he  applied  him- 
self with  ardor  and  sagacity  to  the  study  of  the  fine  structure 
of  the  different  parts  of  the  body,"  and  he  extended  his  inves- 
itgations  to  the  structure  of  plants  and  of  different  animals, 
and  also  to  their  development.  Entering,  as  he  did,  a  new 
and  unexplored  territory,  naturally  he  made  many  discover- 
ies, but  no  man  of  mean  talents  could  have  done  his  work. 

Activity  in  Research. — During  forty  years  of  his  life  he 
was  always  busy  with  research.  Many  of  his  discoveries  had 
practical  bearing  on  the  advance  of  anatomy  and  physiology 
as  related  to  medicine.  In  1661  he  demonstrated  the  struc- 
ture of  the  lungs.  Previously  these  organs  had  been  regarded 
as  a  sort  of  homogeneous  parenchyma.  He  showed  the  pres- 
ence of  air-cells,  and  had  a  tolerably  correct  idea  of  how  the 
air  and  the  blood  are  brought  together  in  the  lungs,  the  two 
never  actually  in  contact,  but  always  separated  by  a  mem- 
brane. These  discoveries  were  first  made  on  the  frog,  and 
applied  by  analogy  to  the  interpretation  of  the  lungs  of  the 
human  body.  He  was  a  comparative  anatomist,  and  the 
first  to  insist  on  analogies  of  structure  between  organs 
throughout  the  animal  kingdom,  and  to  make  extensive 
practical  use  of  the  idea  that  discoveries  on  simpler  animals 
can  be  utilized  in  interpreting  the  similar  structures  in  the 
higher  ones. 


INTRODUCTION    OF    THE    MICROSCOPE  63, 

It  is  very  interesting  to  note  that  in  connection  with  this, 
work  he  actually  observed  the  passage  of  blood  through  the 
capillaries  of  the  transparent  lungs  of  the  frog,  and  also  in 
the  mesenter)\  Although  this  antedates  the  similar  obser- 
vations of  Leeuwenhoek  (1669),  nevertheless  the  work  of 
Leeuwenhoek  was  much  more  complete,  and  he  is  usually 
recognized  in  physiology  as  the  discoverer  of  the  capillary 
connection  between  arteries  and  veins.  At  this  same  period 
^lalpighi  also  observed  the  blood  corpuscles. 

Soon  after  he  demonstrated  the  mucous  layer,  or  pigment- 
ary layer  of  the  skin,  intermediate  between  the  true  and  the 
scarf  skin.  He  had  separated  this  layer  by  boiling  and 
maceration,  and  described  it  as  a  reticulated  membrane.. 
Even  its  existence  was  for  a  long  time  controverted,  but  it 
remains  in  modern  anatomy  under  the  title  of  the  Malpighian. 
kyer. 

His  observation  of  glands  was  extensive,  and  while  it  must 
be  confessed  that  many  of  his  conclusions  in  reference  to. 
glandular  structure  were  erroneous,  he  left  his  name  connected 
with  the  Malpighian  corpuscles  of  the  kidney  and  of  the 
spleen.  He  was  also  the  first  to  indicate  the  nature  of  the 
papillae  on  the  tongue.  The  foregoing  is  a  respectable  list  of 
discoveries,  but  much  more  stands  to  his  credit.  Those  which 
follow  have  a  bearing  on  comparative  anatomy,  zoology,  and 
botany. 

Monograph  on  the  Structure  and  Metamorphosis  of  the 
Silkworm. — Malpighi's  work  on  the  structure  of  the  silkworm 
takes  rank  among  the  most  famous  monographs  on  the 
anatomy  of  a  single  animal.  Much  skill  was  required  to 
give  to  the  world  this  picture  of  minute  structure.  The  mar- 
vels of  organic  architecture  were  being  made  known  in  the 
human  body  and  the  higher  animals,  but  ''no  insect — ^hardly, 
indeed,  any  animal — had  then  been  carefully  described,  and 
all  the  methods  of  the  work  had   to  be  discovered."     He 


64  BIOLOGY   AND    ITS    MAKERS 

labored  with  such  enthusiasm  in  this  new  territory  as  to  throw 
himself  into  a  fever  and  to  set  up  an  inflammation  in  the  eyes. 
"Nevertheless,"  says  Malpighi,  "  in  performing  these  re- 
searches so  many  marvels  of  nature  were  spread  before  my 
eyes  that  I  experienced  an  internal  pleasure  that  my  pen 
could  not  describe." 

He  showed  that  the  method  of  breathing  was  neither  by 
lungs  nor  by  gills,  but  through  a  system  of  air-tubes,  com- 
municating with  the  exterior  through  buttonhole  shaped 
openings,  and,  internally,  by  an  infinitude  of  branches  reach- 
ing to  the  minutest  parts  of  the  body.  Malpighi  showed  an 
instinct  for  comparison;  instead  of  confining  his  researches 
to  the  species  in  hand,  he  extended  his  observations  to  other 
insects,  and  has  given  sketches  of  the  breathing-tubes,  held 
open  by  their  spiral  thread,  taken  from  several  species. 

The  nervous  system  he  found  to  be  a  central  white  cord 
with  swellings  in  each  ring  of  the  body,  from  which  nerves 
are  given  off  to  all  organs  and  tissues.  The  cord,  which  is,  of 
course,  the  central  nervous  system,  he  found  located  mainly 
on  the  ventral  surface  of  the  body,  but  extending  by  a  sort 
of  collar  of  nervous  matter  around  the  oesophagus,  and  on 
the  dorsal  surface  appearing  as  a  more  complex  mass,  or 
brain,  from  which  nerves  are  given  off  to  the  eyes  and  other 
sense  organs  of  the  head.  As  illustrations  from  this  mono- 
graph we  have,  in  Fig.  14,  reduced  sketches  of  the  drawings 
of  the  nervous  system  and  the  food  canal  in  the  adult  silk- 
worm. The  sketch  at  the  right  hand  illustrates  the  central 
nerve  cord  with  its  ganglionic  enlargement  in  each  segment, 
the  segments  being  indicated  by  the  rows  of  spiracles  at  the 
sides.  The  original  drawing  is  on  a  much  larger  scale, 
and  reducing  it  takes  away  some  of  its  coarseness.  All 
of  his  drawings  lack  the  finish  and  detail  of  Swammerdam's 
work. 

He  showed  also  the  food  canal  and  the  tubules  connected 


INTRODUCTION    OF   THE    MICROSCOPE 


6S 


with  the  intestine,  which  retain  his  name  in  the  insect  anatomy 
of  to-day,  under  the  designation  of  Malpighian  tubes.  The 
silk-forming  apparatus  was  also  figured  and  described.    These 


Fig.   14. — From  Malpighi's  Anatomy  of  the  Silkworm,   1669. 


structures  are  represented,  as  Malpighi  drew  them,  on  the 
left  of  Fig.  14. 

This  monograph,  which  was  originally  published  in  1669 
by  the  Royal  Society  of  London,  bears  the  Latin  title,  Disser- 
laiio  Epistolica  de  Bombyce.     It  has  been  several  times  re- 
published, the  best  edition  being  that  in  French,  which  dates 
S 


66  BIOLOGY   AND    ITS    MAKERS 

from  MoRtpellier,  in  1878,  and  which  is  prefaced  by  an 
account  of  the  life  and  labors  of  Malpighi. 

Anatomy  of  Plants. — Malpighi's  anatomy  of  plants  con- 
stitutes one  of  his  best,  as  well  as  one  of  his  most  extensive 
works.  In  the  folio  edition  of  his  works,  1675-79,  the 
Anatome  Plantarum  occupies  not  less  than  152  pages  and 
is  illustrated  by  ninety-three  plates  of  figures.  It  comprises 
an  exposition  of  the  structure  of  bark,  stem,  roots,  seeds,  the 
process  of  germination,  and  includes  a  treatise  on  galls,  etc., 
etc. 

In  this  work  the  microscopic  structure  of  plants  is  amply 
illustrated,  and  he  anticipated  to  a  certain  degree  the  ideas  on 
the  cellular  structure  of  plants.  Burnett  says:  "His  obser- 
vations appear  to  have  been  very  accurate,  and  not  only  did 
he  maintain  the  cellular  structure  of  plants,  but  also  declared 
that  it  was  composed  of  separate  cells,  which  he  designated 
'  utricles.' "  Thus  did  he  foreshadow  the  cell  theory  of  plants 
as  developed  by  Schleiden  in  the  nineteenth  century.  When 
it  came  to  interpretations,  he  made  several  errors.  Applying 
his  often-asserted  principle  of  analogies,  he  concluded  that 
the  vessels  of  plants  are  organs  of  respiration  and  of  circula- 
tion, from  a  certain  resemblance  that  they  bear  to  the  breath- 
ing-tubes of  insects.  But  his  observations  on  structure  are 
good,  and  if  he  had  accomplished  nothing  more  than  this 
work  on  plants  he  would  have  a  place  in  the  history  of  botany. 

Work  in  Embryology. — Difficult  as  was  his  task  in  insect 
anatomy  and  plant  histology,  a  more  difficult  one  remains  to 
be  mentioned,  viz.,  his  observations  of  the  develo])ment  of 
animals.  He  had  pushed  his  researches  into  the  finer  struc- 
ture of  organisms,  and  now  he  attempted  to  answer  this 
question:  How  does  one  of  these  organisms  begin  its  life, 
and  by  what  series  of  steps  is  its  body  built  up?  He  turned 
to  the  chick,  as  the  most  available  form  in  which  to  get  an 
insight  into  this  process,  but  he  could  not  extend  his  obser- 


INTRODUCTION    OF   THE    MICROSCOPE  67 

vations  successfully  into  periods  earlier  than  about  the 
twenty-four-hour  stage  of  development.  Two  memoirs  were 
written  on  this  subject,  both  in  1672,  which  were  published 
by  the  Royal  Society  of  England  under  the  titles  De  Forma- 
tione  Pulli  in  Ovo  and  De  Ovo  Incubato.  Of  all  Malpighi's 
work,  this  has  received  the  least  attention  from  reviewers, 
but  it  is,  for  his  time,  a  very  remarkable  achievement.  No 
one  can  look  over  the  ten  folio  plates  without  being  impressed 
wdth  the  extent  and  accuracy  of  his  observations.  His 
sketches  arc  of  interest,  not  only  to  students  of  embryology, 
but  also  to  educated  people,  to  see  how  far  observations 
regarding  the  development  of  animals  had  progressed  in  1672. 
Further  consideration  of  his  position  in  embryology  will  be 
found  in  the  chapter  on  the  rise  of  that  subject. 

Little  is  known  regarding  the  form  of  microscope  em- 
ployed by  Malpighi.  Doubtless,  much  of  his  work  was  done 
wdth  a  simple  lens,  since  he  speaks  of  examining  the  dried 
lungs  with  a  microscope  of  a  single  lens  against  the  hori- 
zontal sun;  but  he  is  also  known  to  have  observed  with  an 
instrument  consisting  of  two  lenses. 

Malpighi  was  a  naturalist,  but  of  a  new  type;  he  began  to 
look  below  the  surface,  and  essayed  a  deeper  level  of  analysis 
in  observing  and  describing  the  internal  and  minute  structure 
of  animals  and  plants,  and  when  he  took  the  further  step  of 
investigating  their  development  he  was  anticipating  the  work 
of  the  nineteenth  century. 

Jan  Swammerdam  (163  7-1 680) 

Swammerdam  was  a  different  type  of  man— nervous, 
incisive,  very  intense,  stubborn,  and  self-willed.  Much  of  his 
character  shows  in  the  portrait  by  Rembrandt  represented 
in  Fig.  15.  Although  its  authenticity  has  been  questioned, 
it  is  the  only  known  portrait  of  Swammerdam. 


68  BIOLOGY    AND    ITS    MAKERS 

Early  Interest  in  Natural  History. — He  was  born  in  1637, 
nine  years  after  Malpighi.  His  father,  an  apothecary  of  Am- 
sterdam, had  a  taste  for  collecting,  which  was  shared  by  many 
of  his  fellow-townsmen.  The  Dutch  people  of  this  time 
sent  their  ships  into  all  parts  of  the  world,  and  this  vast  com- 
merce, together  with  their  extensive  colonial  possessions, 
fostered  the  formation  of  private  museums.  The  elder 
Swammerdam  had  the  finest  and  most  celebrated  collection 
in  all  Amsterdam.  This  was  stored,  not  only  with  treasures, 
showing  the  civilization  of  remote  countries,  but  also  with 
specimens  of  natural  history,  for  which  he  had  a  decided 
liking.  Thus  ''from  the  earliest  dawn  of  his  understanding 
the  young  Swammerdam  was  surrounded  by  zoological 
specimens,  and  from  the  joint  influence,  doubtless,  of  hered- 
itary taste  and  early  association,  he  became  passionately 
devoted  to  the  study  of  natural  history." 

Studies  Medicine. — His  father  intended  him  for  the 
church,  but  he  had  no  taste  for  theology,  though  he  became 
a  fanatic  in  religious  matters  toward  the  close  of  his  life; 
at  this  period,  however,  he  could  brook  no  restraint  in  word 
or  action.  He  consented  to  study  medicine,  but  for  some 
reason  he  was  twenty-six  years  old  before  entering  the  Uni- 
versity of  Leyden.  This  delay  was  very  likely  owing  to  his 
precarious  health,  but, in  the  mean  time,  he  had  not  been  idle; 
he  had  devoted  himself  to  observation  and  study  with  great 
ardor,  and  had  already  become  an  expert  in  minute  dissec- 
tion. When  he  went  to  the  University  of  Leyden,  therefore, 
he  at  once  took  high  rank  in  anatomy.  Anything  demanding 
fine  manipulation  and  dexterity  was  directly  in  his  line.  He 
continued  his  studies  in  Paris,  and  about  1667  took  his  degree 
of  Doctor  of  Medicine. 

During  this  period  of  medical  study  he  made  some  rather 
important  observations  in  human  anatomy,  and  introduced 
the  method  of  injection    that  was    afterward    claimed  bv 


Fig.    15. SWAMMERDAM,    1637-1680. 


70  BIOLOGY    AND    ITS    MAKERS 

Ruysch.  In  1664  he  discovered  the  valves  of  lymphatic 
vessels  by  the  use  of  slender  glass  tubes,  and,  three  years 
later,  first  used  a  waxy  material  for  injecting  blood-vessels. 

It  should  be  noted,  in  passing,  that  Swammerdam  was  the 
first  to  observe  and  describe  the  blood  corpuscles.  As  early 
as  1658  he  described  them* in  the  blood  of  the  frog,  but  not 
till  fifty-seven  years  after  his  death  were  his  observations 
published  by  Boerhaave,  and,  therefore,  he  does  not  get  the 
credit  of  this  discovery.  Publication  alone,  not  first  observa- 
tion, establishes  priority,  but  there  is  conclusive  evidence 
that  he  observed  the  blood  corpuscles  before  either  Malpighi 
or  Leeuwenhoek  had  published  his  findings. 

Love  of  Minute  Anatomy. — ^After  graduating  in  medi- 
cine he  did  not  practice,  but  followed  his  strong  inclination 
to  devote  himself  to  minute  anatomy.  This  led  to  differences 
with  his  father,  who  insisted  on  his  going  into  practice,  but 
the  self-willed  stubbornness  and  firmness  of  the  son  now 
shov/ed  themselves.  It  was  to  gratify  no  love  of  ease  that 
Swammerdam  thus  held  out  against  his  father,  but  to  be 
able  to  follow  an  irresistible  leading  toward  minute  anatomy. 
At  last  his  father  planned  to  stop  supplies,  in  order  to  force 
him  into  the  desired  channel,  but  Swammerdam  made  efforts, 
without  success,  to  sell  his  own  personal  collection  and  pre- 
serve his  independence.  His  father  died,  leaving  him  suffi- 
cient property  to  live  on,  and  brought  the  controversy  to  a 
close  soon  after  the  son  had  consented  to  yield  to  his  wishes. 

Boerhaave,  his  fellow-countryman,  gathered  Swammer- 
dam's  complete  writings  after  his  death  and  published  them 
in  1737  under  the  title  Bihlia  Naturce.  With  them  is  in- 
cluded a  life  of  Swammerdam,  in  which  a  graphic  account  is 
given  of  his  phenomenal  industry,  his  intense  application,  his 
methods  and  instruments.  Most  of  the  following  passages 
are  selected  from  that  work. 

Intensity   as    a  Worker. — He  was  a  very   intemperate 


INTRODUCTION    OF    THE    MICROSCOPE  7^ 

worker,  and  in  finishing  his  treatise  on  bees  (1673)  ^^  broke 
himself  down. 

"It  was  an  undertaking  too  great  for  the  strongest  con- 
stitution to  be  continually  employed  by  day  in  making  obser- 
vations and  almost  as  constantly  engaged  by  night  in  record- 
ing til  em  by  drawings  and  suitable  explanations.  This  being 
summer  work,  his  daily  labors  began  at  six  in  the  morning, 
when  the  sun  afforded  him  light  enough  to  enable  him  to 
survey  such  minute  objects;  and  from  that  time  till  twelve 
he  continued  without  interruption,  all  the  while  exposed  in 
the  open  air  to  the  scorching  heat  of  the  sun,  bareheaded, 
for  fear  of  interrupting  the  light,  and  his  head  in  a  manner 
dissolving  into  sw^eat  under  the  irresistible  ardors  of  that 
powerful  luminary.  And  if  he  desisted  at  noon,  it  was  only 
because  the  strength  of  his  eyes  was  too  much  weakened  by 
the  extraordinary  efflux  of  light  and  the  use  of  microscopes 
to  continue  any  longer  upon  such  small  objects. 

"This  fatigue  our  author  submitted  to  for  a  whole  month 
together,  without  any  interruption,  merely  to  examine,  de- 
scribe, and  represent  the  intestines  of  bees,  besides  many 
months  more  bestowed  upon  the  other  parts ;  during  which 
time  he  spent  whole  days  in  making  observations,  as  long  as 
there  was  sufficient  light  to  make  any,  and  whole  nights  in 
registering  his  observations,  till  at  last  he  brought  his  treatise 
on  bees  to  the  wished-for  perfection." 

Method  of  Work. — "For  dissecting  very  minute  objects,  he 
had  a  brass  table  made  on  purpose  by  that  ingenious  artist, 
Samuel  Musschenbroek.  To  this  table  were  fastened  two 
brass  arms,  movable  at  pleasure  to  any  part  of  it,  and  the 
up])er  portion  of  these  arms  was  likewise  so  contrived  as  to 
be  susceptible  of  a  very  slow  vertical  motion,  by  which  means 
the  operator  could  readily  alter  their  height  as  he  saw  most 
convenient  to  his  purpose.  The  ofhce  of  one  of  these  arms 
was  to  hold  the  little  corpuscles,  and  that  of  the  other  to  apply 


72  BIOLOGY   AND    ITS    MAKERS 

the  microscope.  His  microscopes  were  of  various  sizes  and 
curvatures,  his  microscopical  glasses  being  of  various  diam- 
eters and  focuses,  and,  from  the  least  to  the  greatest,  the  best 
that  could  be  procured,  in  regard  to  the  exactness  of  the  work- 
manship and  the  transparency  of  the  substance. 

"But  the  constructing  of  very  fine  scissors,  and  giving 
them  an  extreme  sharpness,  seems  to  have  been  his  chief 
secret.  These  he  made  use  of  to  cut  very  minute  objects, 
because  they  dissected  them  equably,  whereas  knives  and 
lancets,  let  them  be  ever  so  fine  and  sharp,  are  apt  to  disorder 
delicate  substances.  His  knives,  lancets,  and  styles  were  so 
fine  that  he  could  not  see  to  sharpen  them  without  the  assist- 
ance of  the  microscope;  but  with  them  he  could  dissect  the 
intestines  of  bees  with  the  same  accuracy  and  distinctness 
that  others  do  those  of  large  animals. 

"He  was  particularly  dexterous  in  the  management  of 
small  tubes  of  glass  no  thicker  than  a  bristle,  drawn  to  a  very 
fine  point  at  one  end,  but  thicker  at  the  other." 

These  were  used  for  inflating  hollow  structures,  and  also 
for  making  fine  injections.  He  dissolved  the  fat  of  insects 
in  turpentine  and  carried  on  dissections  under  water. 

An  unbiased  examination  of  his  work  will  show  that  it  is 
of  a  higher  quality  than  Malpighi's  in  regard  to  critical 
observation  and  richness  of  detail.  He  also  worked  with 
minuter  objects  and  displayed  a  greater  skill. 

The  Religious  Devotee. — The  last  part  of  his  life  was 
dimmed  by  fanaticism.  He  read  the  works  of  Antoinette 
Bourignon  and  fell  under  her  influence;  he  began  to  subdue 
his  warm  and  stubborn  temper,  and  to  give  himself  up  to 
religious  contemplation.  She  taught  him  to  regard  scientific 
research  as  worldly,  and,  following  her  advice,  he  gave  up  his 
passionate  fondness  for  studying  the  works  of  the  Creator, 
to  devote  himself  to  the  love  and  adoration  of  that  same 
Being.     Always  extreme  and  intense  in  everything  he  under- 


INTRODUCTION    OF   THE    MICROSCOPE 


13 


took,  he  likewise  overdid  this,  and  yielded  himself  to  a  sort 
of  fanatical  worship  until  the  end  of  his  life,  in  1680.  Had 
he  possessed  a  more  vigorous  constitution  he  would  have 
been  greater  as  a  man.  He  lived,  in  all,  but  forty-three  years ; 
the  last  six  or  seven  years  were  unproductive  because  of  his 
mental  distractions,  and  before  that,  much  of  his  time  had 
been  lost  through  sickness. 

The  Biblia  Naturae. — It  is  time  to  ask,  What,  with  all  his 
talents  and  prodigious  application,  did  he  leave  to  science? 
This  is  best  answered  by  an  examination  of  the  Biblia  Na~ 
lurcB,  under  which  title  all  his  work  was  collected.  His  treatise 
on  Bees  and  Mayflies  and  a  few  other  articles  were  pub- 
lished during  his  lifetime,  but  a  large  part  of  his  observations 
remained  entirely  unknown  until  they  were  published  in  this 
book  fifty-seven  years  after  his  death.  In  the  folio  edition 
(1737-1738)  it  embraces  410  pages  of  text  and  fifty-three 
plates,  replete  with  figures  of  original  observations.  It  *'  con- 
tains about  a  dozen  life-histories  of  insects  worked  out  in  more 
or  less  detail.  Of  these,  the  mayfly  is  the  most  famous,  that  on 
the  honey-bee  the  most  elaborate."  The  greater  amount  of 
his  work  was  in  structural  entomology.  It  is  known  that  he 
had  a  collection  of  about  three  thousand  different  species  of 
insects,  which  for  that  period  was  a  very  large  one.  There 
is,  however,  a  considerable  amount  of  work  on  oth  er  animals ; 
the  fine  anatomy  of  the  snail,  the  structure  of  the  clam,  the 
squid;  observations  on  the  structure  and  development  of  the 
frog;  observations  on  the  contraction  of  the  muscles,  etc.,  etc. 

It  is  to  be  remembered  that  Swammerdam  was  extremely 
exact  in  all  that  he  did.  His  descriptions  are  models  of 
accuracy  and  completeness. 

Fig.  16  shows  reduced  sketches  of  his  illustrations  of  the 
structure  of  the  snail.  The  upper  sketch  shows  the  central 
nervous  system  and  the  nerve  trunks  connected  therev/ith, 
and  the  lower  figure  shows  the  shell  and  the  principal  muscles. 


Fig.   i6. — From  Swammerdam's  Bihlia  NaturcB. 


INTRODUCTION    OF   THE    MICROSCOPE  75 

This  is  an  exceptionally  good  piece  of  anatomization  for  that 
time,  and  is  a  fair  sample  of  the  fidelity  with  which  he  worked 
out  details  in  the  structure  of  small  animals.  Besides  show- 
ing this,  these  figures  also  serve  the  purpose  of  pointing  out 
that  Swammerdam's  fine  anatomical  work  was  by  no  means 
confined  to  insects.  His  determinations  on  the  structure  of 
the  young  frog  were  equally  noteworthy. 

But  we  should  have  at  least  one  illustration  of  his  handling 
of  insect  anatomy  to  compare  more  directly  with  that  of 
Malpighi,  already  given.  Fig.  17  is  a  reduced  sketch  of  the 
anatomy  of  the  larva  of  an  ephemerus,  showing,  besides  other 
structures,  the  central  nervous  system  in  its  natural  position. 
When  compared  with  the  drawings  of  Malpighi,  we  see  there 
is  a  more  masterly  hand  at  the  task,  and  a  more  critical  spirit 
back  of  the  hand.  The  nervous  system  is  very  well  done, 
and  the  greater  detail  in  other  features  shows  a  disposition 
to  go  into  the  subject  more  deeply  than  Malpighi. 

Besides  working  on  the  structure  and  life-histories  of  ani- 
mals, Swammerdam  showed,  experimentally,  the  irritability 
of  nerves  and  the  response  of  muscles  after  their  removal 
from  the  body.  He  not  only  illustrates  this  quite  fully,  but 
seems  to  have  had  a  pretty  good  appreciation  of  the  nature 
of  the  problem  of  the  physiologist.     He  says : 

*'  It  is  evident  from  the  foregoing  observations  that  a  great 
number  of  things  concur  in  the  contraction  of  the  muscles, 
and  that  one  should  be  thoroughly  acquainted  with  that 
wonderful  machine,  our  body,  and  the  elements  with  which 
we  are  surrounded,  to  describe  exactly  one  single  muscle 
and  explain  its  action.  On  this  occasion  it  would  be  neces- 
sary for  us  to  consider  the  atmosphere,  the  nature  of  our  food, 
the  blood,  the  brain,  marrow,  and  nerves,  that  most  subtle 
matter  which  instantaneously  flows  to  the  fibers,  and  many 
other  things,  before  we  could  expect  to  attain  a  sight  of  the 
perfect  and  certain  truth." 


Fig.    17. — Anatomy    of    an    Insect:     Dissected    and    Drawn     by 
Swammerdam. 


INTRODUCTION    OF    THE    MICROSCOPE  77 

In  reference  to  the  formation  of  animals  within  the  egg, 
Swammerdam  was,  as  Malpighi,  a  believer  in  the  prc-forma- 
tion  theory.  The  basis  for  his  position  on  this  question  will 
be  set  forth  in  the  chapter  on  the  Rise  of  Embryology. 

There  was  another  question  in  his  time  upon  which  philos- 
ophers and  scientific  men  were  divided,  which  was  in  reference 
to  the  origin  of  living  organisms:  Does  lifeless  matter,  some- 
times, when  submitted  to  heat  and  moisture,  spring  into  life  ? 
Did  the  rats  of  Egypt  come,  as  the  ancients  believed,  from 
the  mud  of  the  Nile,  and  do  frogs  and  toads  have  a  similar 
origin  ?  Do  insects  spring  from  the  dew  on  plants  ?  etc.,  etc. 
The  famous  Redi  performed  his  noteworthy  experiments 
when  Swammerdam  was  twenty-eight  years  old,  but  opinion 
was  divided  upon  the  question  as  to  the  possible  spontaneous 
origin  of  life,  especially  among  the  smaller  animals.  Upon 
this  question  Swammerdam  took  a  positive  stand;  he  ranged 
himself  on  the  side  of  the  more  scientific  naturalists  against 
the  spontaneous  formation  of  life. 

Antony  van  Leeuwtn'hoek  (1632-1723) 

In  Eeeuwenhoek  we  find  a  composed  and  better-balanced 
man.  Blessed  with  a  vigorous  constitution,  he  lived  ninety- 
one  years,  and  worked  to  the  end  of  his  life.  He  was  bom 
in  1632,  four  years  after  Malpighi,  and  five  before  Swammer- 
dam; they  were,  then,  strictly  speaking,  contemporaries. 
He  stands  in  contrast  with  the  other  men  in  being  self-taught; 
he  did  not  have  the  advantage  of  a  university  training,  and 
apparently  never  had  a  master  in  scientific  study.  This  lack 
of  systematic  training  shows  in  the  desultory  character  of  his 
extensive  observations.  Impelled  by  the  same  gift  of  genius 
that  drove  his  confreres  to  study  nature  with  such  unexampled 
activity,  he  too  followed  the  path  of  an  independent  and 
enthusiastic  investigator. 


78  BIOLOGY   AND    ITS    MAKERS 

The  portrait  (Fig.  i8)  which  forms  a  frontispiece  to  his 
Arcana  Natures  represents  him  at  the  age  of  sixty-three, 
and  shows  the  pleasing  countenance  of  a  firm  man  in  vigor- 
ous health.  Richardson  says:  "In  the  face  peering  through 
the  big  wig  there  is  the  quiet  force  of  Cromwell  and  the 
delicate  disdain  of  Spinoza."  "It  is  a  mixed  racial  type, 
Semitic  and  Teutonic,  a  Jewish-Saxon;  obstinate  and  yet 
imaginative;  its  very  obstinacy  a  virtue,  saving  it  from  flying 
too  far  wild  by  its  imagination." 

Recent  Additions  to  His  Biography. — There  was  asingular 
scarcity  of  facts  in  reference  to  Leeuwenhoek's  life  until  1885, 
when  Dr.  Richardson  published  in  TheAsclepiad  *  the  results 
of  researches  made  by  Mr.  A.  Wynter  Blyth  in  Leeuwenhoek's 
native  town  of  Delft.  I  am  indebted  to  that  article  for  much 
that  follows. 

His  Arcana  Natures  and  other  scientific  letters  contained 
a  complete  record  of  his  scientific  activity,  but  "about  his 
parentage,  his  education,  and  his  manner  of  making  a  living 
there  was  nothing  but  conjecture  to  go  upon."  The  few 
scraps  of  personal  history  were  contained  in  the  PLncyclo- 
paedia  articles  by  Carpenter  and  others,  and  these  were 
wrong  in  sustaining  the  hypothesis  that  Teeuwenhoek  was 
an  optician  or  manufacturer  of  lenses  for  the  market.  Al- 
though he  ground  lenses  for  his  own  use,  there  was  no  need 
on  his  part  of  increasing  his  financial  resources  by  their  sale. 
He  held  under  the  court  a  minor  ofhce  designated  '  Chamber- 
lain of  the  Sheriff.'  The  duties  of  the  office  were  those  of  a 
beadle,  and  were  set  forth  in  his  commission,  a  document 
still  extant.  The  requirements  were  light,  as  was  also  the 
salary,  w^hich  amounted  to  about  £26  2i  year.  He  held  this 
post  for  thirty-nine  years,  and  the  stipend  was  thereafter 
continued  to  him  to  the  end  of  his  life. 

Van  Leeuwenhoek  was  derived  from  a  good  Delft  family. 

*  Leeuwenhoek  and  the  Rise  of  Histology.   The  Asclepiad,  Vol.  II,  1885. 


Fig.   i8. — Leeuwenhoek,   1632-1723. 


8o  BIOLOGY   AND    ITS    MAKERS 

His  grandfather  and  his  great-grandfather  were  Delft  brewers, 
and  his  grandmother  a  brewer's  daughter.  The  family  were 
doubtless  wealthy.  His  schooling  seems  to  have  been  brought 
to  a  close  at  the  age  of  sixteen,  when  he  was  ''  removed  to  a 
clothing  business  in  Amsterdam,  where  he  filled  the  office  of 
bookkeeper  and  cashier."  After  a  few  years  he  returned  to 
Delft,  and  at  the  age  of  twenty-two  he  married,  and  gave 
himself  up  largely  to  studies  in  natural  history.  Six  years 
after  his  marriage  he  obtained  the  appointment  mentioned 
above.  He  was  twice  married,  but  left  only  one  child,  a 
daughter  by  his  first  wife.  In  the  old  church  at  Delft  is  a 
monument  erected  by  this  daughter  to  the  memory  of  her 
father. 

He  led  an  easy,  prosperous,  but  withal  a  busy  life.  The 
microscope  had  recently  been  invented,  and  for  observation 
with  that  new  instrument  Leeuwenhoek  showed  an  avidity 
amounting  to  a  passion. 

''That  he  was  in  comfortable,  if  not  affluent,  circum- 
stances is  clear  from  the  character  of  his  writings;  that  he 
was  not  troubled  by  any  ver}^  anxious  and  responsible  duties 
is  certain  from  the  continuity  of  his  scientific  work;  that  he 
could  secure  the  services  of  persons  of  influence  is  discernible 
from  the  circumstances  that,  in  1673,  De  Graaf  sent  his  first 
paper  to  the  Royal  Society  of  London;  that  in  1680  the  same 
society  admitted  him  as  fellow;  that  the  directors  of  the  East 
India  Company  sent  him  specimens  of  natural  history,  and 
that,  in  1698,  Peter  the  Great  paid  him  a  call  to  inspect  his 
microscopes  and  their  revelations." 

Leeuwenhoek  seems  to  have  been  fascinated  by  the  mar- 
vels of  the  microscopic  world,  but  the  extent  and  quality  of 
his  work  lifted  him  above  the  level  of  the  dilettante.  He 
was  not,  like  Malpighi  and  Swammerdam,  a  skilled  dissector, 
but  turned  his  microscope  in  all  directions;  to  the  mineral 
as  well  as  to  the  vegetable  and  animal  kingdoms.     Just  when 


INTRODUCTION    OF   THE    MICROSCOPE  8l 

he  began  to  use  the  microscope  is  not  known;  his  first  pub- 
lication in  reference  to  microscopic  objects  did  not  appear 
till  1673,  when  he  was  forty-one  years  old. 

His  Microscopes. — He  gave  good  descriptions  and  draw- 
ings of  his  instruments,  and  those  still  in  existence  have  been 
described  by  Carpenter  and  others,  and  in  consequence  we 
have  a  very  good  idea  of  his  working  equipment.  During 
his  lifetime  he  sent  as  a  present  to  the  Royal  Society  of 
London  twenty-six  microscopes,  each  provided  with  an  object 
to  examine.  Unfortunately,  these  were  removed  from  the 
rooms  of  the  society  and  lost  during  the  eighteenth  century. 
His  lenses  v/ere  of  fine  quality  and  were  ground  by  himself. 
They  were  nearly  all  simple  lenses,  of  small  size  but  con- 
siderable curvature,  and  needed  to  be  brought  close  to  the 
object  examined.  He  had  different  microscopes  for  different 
purposes,  giving  a  range  of  magnifying  powers  from  40  to  270 
diameters  and  possibly  higher.  The  number  of  his  lenses  is 
surprising;  he  possessed  not  less  than  247  complete  micro- 
scopes, two  of  which  were  provided  with  double  lenses,  and 
one  with  a  triplet.  In  addition  to  the  above,  he  had  172 
lenses  set  between  plates  of  metal,  which  give  a  total  of  419 
lenses  used  by  him  in  his  observations.  Three  were  of 
quartz,  or  rock  crystal;  the  rest  were  of  glass.  More  than 
one-half  the  lenses  were  mounted  in  silver;  three  were  in 
gold. 

It  is  to  be  understood  that  all  his  microscopes  were  of 
simple  construction;  no  tubes,  no  mirror;  simple  pieces 
of  metal  to  hold  the  magnifying-glass  and  the  objects  to 
be  examined,  with  screws  to  adjust  the  position  and  the 
focus. 

The  three  aspects  of  one  of  Leeuwenhoek's  microscopes 

shown  in  Fig.  19  will  give  a  very  good  idea  of  how  they  were 

constructed.     These  pictures  represent    the  actual   size  of 

the  instrument.     The  photographs  were  made  by  Professor 

6 


82 


BIOLOGY    AND    ITS    MAKERS 


Nierstrasz  from  the  specimen  in  possession  of  the  University 
of  Utrecht.  The  instrument  consists  of  a  double  copper  plate 
in  which  the  circular  lens  is  inserted,  and  an  object-holder — ■ 
represented  in  the  right-hand  lower  figure  as  thrown  to  one 


Fig.   19. — Leeuwenhoek's  ^Microscope. 
Natural  size.    From  Photographs  by  Professor  Nierstrasz,  of  Utrecht. 


side.  By  a  vertical  screw  the  object  could  be  elevated  or 
depressed,  and  by  a  transverse  screw  it  could  be  brought 
nearer  or  removed  farther  from  the  lens,  and  thus  be  brought 
into  focus. 

Fig.  20a  shows  the  way  in  which  the  microscope  was 


INTRODUCTION    OF    THE    MICROSCOPE 


83 


arranged  to  examine  the  circulation  of  blood  in  the  trans- 
parent tail  of  a  small  fish.  The  fish  was  'placed  in 
water  in  a  slender  glass  tube,  and  the  latter  was  held  in  a 
metallic  frame,  to  which  a 
plate  (marked  D)  was  joined, 
carrying  the  magnifying 
glass.  The  latter  is  indi- 
cated in  the  circle  above  the 
letter  D,  near  the  tail- fin  of 
the  fish.  The  eye  was  ap- 
plied close  to  this  circular 
magnifying-glass,  which  was 
brought  into  position  and 
adjusted  by  means  of  screws. 
In  some  instances,  he  had  a 
concave  reflector  with  a  hole 
in  the  center,  in  which  his 
magnifying-glass  was  insert- 
ed; in  this  form  of  instru- 
ment the  objects  were  illu- 
mined by  reflected,  and  not 
by  transmitted  light. 

His  Scientific  Letters. — 
His  microscopic  observations 
were  described  and  sent  to 
learned  societies  in  the  form 
of  letters.  "  All  or  nearly  all 
that  he  did  in  a  literary  way 
was  after  the  manner  of  an 
epistle,"  and  his  written  com- 
munications were  so  numer- 
ous as  to  justify  the  cogno- 
men, "The  man  of  many  ,,  Fjg.  20a.  —  Leeuwenhoek's 
1  ^.  n  urr-i  T-  1  A  1  Mechanism  for  Examining  the 
letters."     '' The  French  x\cad-      Circulation  of  the  Blood. 


84 


BIOLOGY   AND    ITS    MAKERS 


emy  of  Sciences,  of  which  he  was  elected  a  corresponding 
member  in  1697,  got  twenty-seven;  but  the  lion's  share 
fell  to  the  young  Royal  Society  of  London,  which  in  fifty 
years — 1673-1723 — received  375  letters  and  papers."  "  The 
works  themselves,  except  that  they  lie  in  the  domain  of 
natural  history,  are  disconnected  and  appear  in  no  order 
of  systematized  study.  The  philosopher  was  led  by  what 
transpired  at  any  moment  to  lead  him." 

The  Capillary  Circulation. — In  1686  he  obscr^'ed  the 
minute  circulation  of  the  blood,  and  demonstrated  the  capil- 
lary connection  between  arteries  and  veins,  thus  forging  the 

final  link  in  the  chain   of 


/^-     r- 


observation  showing  the 
relation  between  these 
blood-vessels.  This  was 
perhaps  his  most  important 
observation  for  its  bearing 
on  physiology.  It  must  be 
remembered  that  Harvey 
had  not  actually  seen  the 
circulation  of  the  blood, 
which  he  announced  in 
1628.  He  assumed  on  en- 
tirely sufficient  grounds  the 
existence  of  a  complete  cir- 
culation, but  there  was 
wanting  in  his  scheme  the 
direct  ocular  proof  of  the 
passage  of  blood  from  arteries  to  veins.  This  was  supplied 
by  Leeuwenhoek.  Fig.  2oh  shows  one  of  his  sketches  of  the 
capillary  circulation.  In  his  efforts  to  see  the  circulation 
he  tried  various  animals;  the  comb  of  the  young  cock,  the 
ears  of  white  rabbits,  the  membraneous  wing  of  the  bat  w^ere 
progressively  examined.     The  next  advance  came  when  he 


Fig.  206. — The  Capillary  Circula- 
tion.    (After  Leeuwenhoek.) 


INTRODUCTION    OF   THE    MICROSCOPE  85 

directed  his  microscope  to  the  tail  of  the  tadpole.  Upon 
examining  this  he  exclaims: 

"  A  sight  presented  itself  more  delightful  than  any  mine 
eyes  had  ever  beheld ;  for  here  I  discovered  more  than  fifty 
circulations  of  the  blood  in  different  places,  while  the  animal 
lay  quiet  in  the  water,  and  I  could  bring  it  before  my  micro- 
scope to  my  wish.  For  I  saw  not  only  that  in  many  places 
the  blood  was  conveyed  through  exceedingly  minute  vessels, 
from  the  middle  of  the  tail  tovx-ard  the  edges,  but  that  each 
of  the  vessels  had  a  curve  or  turning,  and  carried  the  blood 
back  toward  the  middle  of  the  tail,  in  order  to  be  again  con- 
veyed to  the  heart.  Hereby  it  plainly  appeared  to  me  that 
the  blood-vessels  which  I  now  savv^  in  the  animal,  and  w^hich 
bear  the  names  of  arteries  and  veins  are,  in  fact,  one  and  the 
same;  that  is  to  say,  that  they  are  properly  termed  arteries 
so  long  as  they  convey  the  blood  to  the  f  urtherest  extremities 
of  its  vessels,  and  veins  Vv'hen  they  bring  it  back  to  the  heart. 
And  thus  it  appears  that  an  SLvtery  and  a  vein  are  one  and 
the  same  vessel  prolonged  or  extended." 

This  description  shows  that  he  fully  appreciated  the  course 
of  the  minute  vascular  circulation  and  the  nature  of  the 
communication  between  arteries  and  veins.  He  afterward 
extended  his  observations  to  the  web  of  the  frog's  foot,  the 
tail  of  young  fishes  and  eels. 

In  connection  with  this  it  should  be  remembered  that 
Malpighi,  in  1661,  observ^ed  the  flow  of  blood  in  the  lungs 
and  in  the  mesentery  of  the  frog,  but  he  made  little  of  the 
discovery.  Leeuwenhoek  did  more  with  his,  and  gave  the 
first  clear  idea  of  the  capillary  circulation.  Leeuwenhoek 
was  anticipated  also  by  Malpighi  in  reference  to  the  micro- 
scopic structure  of  the  blood.  (See  also  under  Swammer- 
dam.)  To  Malpighi  the  corpuscles  appeared  to  be  globules 
of  fat,  while  Leeuwenhoek  noted  that  the  blood  disks  of 
birds,  frogs,  and  fishes  were  oval  in  outline,  and  those  of 


86 


BIOLOGY    AND    ITS    MAKERS 


mammals  circular.  He  reserved  the  term  '  globule '  for 
those  of  the  human  body,  erroneously  believing  them  to 
be  spheroidal. 

Other  Discoveries. — Among  his  other  discoveries  bear- 
ing on  physiology  and  medicine  may  be  mentioned:  the 
branched  character  of  heart  muscles,  the  stripe  in  voluntary 
muscles,  the  structure  of  the  crystalline  lens,  the  description 
of  spermatozoa  after  they  had  been  pointed  out  to  him  in 
1674  by  Hamen,  a  medical  student  in  Leyden,  etc.  Richard- 
son dignified  him  with  the  title 'the  founder  of  histology,' 
but  this,  in  view  of  the  work  of  his  great  contemporary, 
Malpighi,  seems  to  me  an  overestimate. 

Turning  his  microscope  in  all  directions,  he  examined 
water  and  found  it  peopled  with  minute  animalcules,  those 
simple  forms  of  animal  life  propelled  through  the  water  by 
innumerable  hair-like  cilia  extending  from  the  body  like 
banks  of  oars  from  a  galley,  except  that  in 
many  cases  they  extend  from  all  surfaces. 
He  saw-  not  only  the  animalcules,  but  also 
the  cilia  that  m.ove  their  bodies. 

He  also  discovered   the  Rotifers,  those 

favorites  of  the  amateur  microscopists,  made 

so  familiar  to  the  general  public  in  works 

like    Gosse's    Evenings    at  the  Microscope. 

He  observed    that    when    water  containing 

these    animalcules 

evaporated  they  were 

reduced  to  fine  dust, 

but     became     alive 

again,    after   great 

lapses  of  time,  by  the 

introduction  of  water. 

Fig.  2 1. —Plant Cells.    (From  Leeuwen-  ^^      ^^^^     ^^^y 

hoek's  Arcana  Natures.)  observations     on     the 


INTRODUCTION    OF   THE    MICROSCOPE  87 

microscopic  structure  of  plants.  Fig.  21  gives  a  fair  sample 
of  the  extent  to  which  he  observed  the  cellular  construction 
of  vegetables  and  anticipated  the  cell  theory.  While  Mal- 
pighi's  research  in  that  field  was  more  extensive,  these 
sketches  from  Lceuwenhoek  represent  very  well  the  char- 
acter of  the  work  of  the  period  on  the  minute  structures 
of  plants. 

His  Theoretical  Views. — It  remains  to  say  that  on  the 
two  biological  questions  of  the  day  he  took  a  decisive  stand. 
He  was  a  believer  in  pre-formation  or  pre-delineation  of  the 
embr}'0  in  an  extreme  degree,  seeing  in  fancy  the  complete 
outline  of  both  maternal  and  paternal  individuals  in  the 
spermatozoa,  and  going  so  far  as  to  make  sketches  of  the 
same.  But  on  the  question  of  the  spontaneous  origin  of  life 
he  took  the  side  that  has  been  supported  with  such  triumphant 
demonstration  in  this  century ;  namely,  the  side  opposing  the 
theory  of  the  occurrence  of  spontaneous  generation  under 
present  conditions  of  life. 

Comparison  of  the  Three  Men. — ^We  see  in  these 
three  gifted  contemporaries  different  personal  characteristics. 
I.eeuwenhoek,  the  composed  and  strong,  attaining  an  age 
of  ninety-one;  Malpighi,  always  in  feeble  health,  but  direct- 
ing his  energies  with  rare  capacity,  reaching  the  age  of  sixty- 
seven  ;  while  the  great  intensity  of  Swammerdam  stopped  his 
scientific  career  at  thirty-six  and  burned  out  his  life  at  the 
age  of  forty-three. 

They  were  all  original  and  accurate  observers,  but  there 
is  variation  in  the  kind  and  quality  of  their  intellectual  prod- 
uct. The  two  university-trained  men  showed  capacity  for 
coherent  observation;  they  were  both  better  able  to  direct 
their  efforts  toward  some  definite  end;  LeeuAvenhoek,  with 
the  advantages  of  vigorous  health  and  long  working  period, 
lacked  the  systematic  training  ot  the  schools,  and  all  his  life 
wrought  in  discursive  fashion;   he  left  no  coherent  piece  of 


88  BIOLOGY   AND    ITS    MAKERS 

work  of  any  extent  like  Malpighi's  Anatome  Planiarum  or 
Swammerdam's  Anatomy  and  Metamorphosis  of  Insects. 

Swammerdam  was  the  most  critical  observer  of  the  three, 
if  we  may  judge  by  his  labors  in  the  same  field  as  Malpighi's 
on  the  silkworm.  His  descriptions  are  models  of  accuracy 
and  completeness,  and  his  anatomical  work  shows  a  higher 
grade  of  finish  and  completeness  than  Malpighi's.  Malpighi, 
it  seems  to  me,  did  more  in  the  sum  total  than  either  of  the 
others  to  advance  the  sciences  of  anatomy  and  physiology, 
and  through  them  the  interests  of  mankind.  Leeuwenhoek 
had  larger  opportunity;  he  devoted  himself  to  microscopic 
observations,  but  he  w^andered  over  the  whole  field.  While 
his  observations  lose  all  monographic  character,  nevertheless 
they  were  important  in  opening  new  fields  and  advancing  the 
sciences  of  anatomy,  physiology,  botany,  and  zoology. 

The  combined  force  of  their  labors  marks  an  epoch 
characterized  by  the  acceptance  of  the  scientific  method  and 
the  establishment  of  a  new  grade  of  intellectual  life.  Th rough 
their  efforts  and  that  of  their  contemporaries  of  lesser  note 
the  new  intellectual  movement  was  now  well  under  way. 


CHAPTER   V 

THE  PROGRESS  OF  MINUTE   ANATOMY. 

The  work  of  Malpighi,  Swammerdam,  and  Leeuwenhoek 
stimulated  investigations  into  the  structure  of  minute  an- 
imals, and  researches  in  that  field  became  a  feature  of  the 
advance  in  the  next  century.  Considerable  progress  was 
made  in  the  province  of  minute  anatomy  before  comparative 
anatomy  grew  into  an  independent  subject. 

The  attractiveness  of  observations  upon  the  life-histories 
and  the  structure  of  insects,  as  shown  particularly  in  the  pub- 
lications of  Malpighi  and  Swammerdam,  made  those  animals 
the  favorite  objects  of  study.  The  observers  were  not  long 
in  recognizing  that  some  of  the  greatest  beauties  of  organic 
architecture  are  displayed  in  the  internal  structure  of 
insects.  The  delicate  tracery  of  the  organs,  their  minuteness 
and  perfection  are  w^ell  calculated  to  awaken  surprise.  Well 
might  those  early  anatomists  be  moved  to  enthusiasm  over 
their  researches.  Every  excursion  into  this  domain  gave 
only  beautiful  pictures  of  a  mechanism  of  exquisite  delicacy, 
and  their  wonder  grew  into  amazement.  Here  began  a  new 
train  of  ideas,  in  the  unexpected  revelation  that  within  the 
small  compass  of  the  body  of  an  insect  w^as  embraced  such 
a  complex  set  of  organs;  a  complete  nervous  system,  fine 
breathing-tubes,  organs  of  circulation,  of  digestion,  etc.,  etc. 

Lyonet. — The  first  piece  of  structural  work  after  Swam- 
merdam's  to  which  we  must  give  attention  is  that  of  Lyonet, 
who  produced  in  the  middle  of  the  eighteenth  century  one  of 

89 


90 


BIOLOGY   AND    ITS    MAKERS 


the  most  noteworthy  monographs  in  the  field  of  minute 
anatomy.  This  was  a  work  like  that  of  Malpighi,  upon  the 
anatomy  of  a  single  form,  but  it  was  carried  out  in  much 


Fig.   22. — Lyonet,   1707-1789. 

greater  detail.     The  137  figures  on  the  18  plates  are  models 
of  close  observation  and  fine  execution  of  drawings. 

Lyonet  (also  written  Lyonnet)  was  a  Hollander,  born  in 
The  Hague  in  1707.  He  was  a  man  of  varied  talents,  a 
painter,  a  sculptor,  an  engraver,  and  a  very  gifted  linguist. 


PROGRESS    OF    MINUTE    ANATOMY  9^ 

It  is  said  that  he  was  skilled  in  at  least  eight  languages;  and 
at  one  time  he  was  the  cipher  secretary  and  confidential 
translator  for  the  United  Provinces  of  Holland.  He  was 
educated  as  a  lawyer,  but,  from  interest  in  the  subject,  de- 
voted most  of  his  time  to  engraving  objects  of  natural  history. 
Among  his  earliest  published  drawings  were  the  figures  for 
Cesser's  Theology  oj  Insects  (1742)  and  for  Trembley's 
famous  treatise  on  Hydra  (1744). 

His  Great  Monograph. — Finally  I>yonet  decided  to  branch 
out  for  himself,  and  produce  a  monograph  on  insect  anatomy. 
After  some  preliminary  work  on  the  sheep-tick,  he  settled 
upon  the  caterpillar  of  the  goat  moth,  which  lives  upon  the 
willow-tree.  His  work,  first  published  in  175c,  bore  the  title 
Traite  Anatomique  de  la  Chenille  qui  ronge  le  hois  de  Saule. 
In  exploring  the  anatomy  of  the  form  chosen,  he  displayed 
not  only  patience,  but  great  skill  as  a  dissector,  while  his 
superiority  as  a  draughtsman  was  continually  shown  in  his 
sketches.  He  engraved  his  own  figures  on  copper.  The  draw- 
ings are  very  remarkable  for  the  amount  of  detail  that  they 
show.  He  dissected  this  form  with  the  same  thoroughness 
with  which  medical  men  have  dissected  the  human  body. 
The  superficial  nmscles  were  carefully  drawn  and  were  then 
cut  away  in  order  to  expose  the  next  underlying  layer  which, 
in  turn,  v/as  sketched  and  then  removed.  The  amount  of 
detail  involved  in  this  work  may  be  in  part  realized  from  the 
circumstance  that  he  distinguished  4,041  separate  muscles. 
His  sketches  show  these  muscles  accurately  drawn,  and  the 
principal  ones  are  lettered.  When  he  came  to  expose  the 
nerves,  he  followed  the  minute  branches  to  individual  small 
muscles  and  sketched  them,  not  in  a  diagrammatic  way,  but 
as  accurate  drawings  from  the  natural  object.  The  breath- 
ing-tubes were  followed  in  the  same  manner,  and  the  other 
organs  of  the  body  were  all  dissected  and  drawn  with  remark- 
able thoroughness.     Lyonet  was  not   trained   in  anatomy 


92 


BIOLOGY   AND    ITS    MAKERS 


like  Malpighi  and  Swammerdam,  but  being  a  man  of  unusual 
patience  and  manual  dexterity,  he  accomplished  notable 
results.  His  great  quarto  volume  is,  however,  mxrely  a  de- 
scription of  the  figures,  and  lacks  the  insight  of  a  trained 
anatomist.  His  skill  as  a  dissector 
is  far  ahead  of  his  knowledge  of 
anatomy,  and  he  becomes  lost  in 
the  details  of  his  subject. 

Extraordinary  Quality  of  the 
Drawings. — ^A  few  figures  will  serve 
to  illustrate  the  character  of  his 
work,  but  the  reduced  reproduc- 
tions which  follow  can  not  do  justice 
to  the  copper  plates  of  the  original. 
Fig.  23  gives  a  view  of  the  exter- 
nal appearance  of  the  caterpillar 
which  was  dissected.  When  the 
skin  was  removed  from  the  outside 
the  muscles  came  into  view,  as 
shown  in  Fig.  24.  This  is  a  view 
from  the  ventral  side  of  the  animal. 
On  the  left  side  the  more  super- 
ficial muscles  show,  and  on  the 
right  the  next  deeper  layer. 

Fig.  25  shows  his  dissection  of 
the  nerves.  In  this  figure  the  mus- 
cles are  indicated  in  outline,  and 
the  distribution  of  nerves  to  partic- 
ular muscles  is  shown. 

Lyonet's  dissection  of  the  head 
is  an  extraordinary  feat.  The  en- 
tire head  is  not  more  than  a  quarter  of  an  inch  in  diam- 
eter, but  in  a  series  of  seven  dissections  he  shows  all  of  the 
internal  organs  in  the  head.     Fig.  26  shows  two  sketches 


1 

1  ■'4.> 

1 

1 

1 

Fig.  23. — Larva  of  the 
Willow  Moth.  (From 
Lyonet's  Monograph, 
1750) 


'-7:'i^'    'I 


Fig.  24. 


Fig.  25. 


Fig.  24.— Muscles  of  the  Larva  of  the  Willow  Moth.     (From 
Lyonet's  Monograph.) 

YiG,  25.— Central  Nervous  System  and  Nerves  of  the  Same. 


94 


BIOLOGY    AND    ITS    MAKERS 


exhibiting  the  nervous  gangha,  the  air  tubes,  and  muscles  of 
the  head  in  their  natural  position. 

Fig.  27  shows  the  nervous  system  of  the  head,  including 
the  extremely  fine  nervous  masses  which  are  designated  the 
sympathetic  nervous  system. 

The  extraordinary  character  of  the  drawings  in  Lyonet's 
monograph  created  a  sensation.  The  existence  of  such  com- 
plicated structures  within  the  body  of  an  insect  was  dis- 


FiG.   26. — Dissection  of  the  Head  of  the  Larva  of  the  Willow  Moth. 


credited,  and,  furthermore,  some  of  his  critics  declared  that 
even  if  such  a  fine  organization  existed,  it  would  be  beyond 
human  possibilities  to  expose  the  details  as  shown  in  his 
sketches.  Accordingly,  Lyonet  was  accused  of  drawing  on 
his  imagination.  In  order  to  silence  his  critics  he  published 
in  the  second  edition  of  his  work,  in  1752,  drawings  of  his 
instruments  and  a  description  of  his  methods. 

Lyonet  intended  to  work  out  the  anatomy  of  the  chrysalis 
and  the  adult  form  of  the  same  animal.     In  pursuance  of 


PROGRESS    OF    MINUTE    ANATOMY 


9S 


this  plan,  he  made  many  dissections  and  drawings,  but,  at 
the  age  of  sixty,  on  account  of  the  condition  of  his  eyes,  he- 
was  obliged  to  stop  all  close  work,  and  his  project  remained 
unfinished.  The  sketches  which  he  had  accumulated  were 
published  later,  but  they  fall  far  short  of  those  illustrating 


1  W:      . 

mm 

1 

ii'iG.  27. — The  Brain  and  Head  Nerves  of  the  Same  Animal. 

the  Traite  Anatomique.     Lyonet  died  in  1789,  at  the  age  of 
eighty-one. 

Roesel,  Reaumur,  and  De  Geer  on  Insect  Life. — ^\Ve  must 
also  take  note  of  the  fact  that,  running  parallel  with  this  work 
on  the  anatomy  of  insects,  observations  and  publications  had 
gone  forward  on  form,  habits,  and  metamorphosis  of  insects, 
that  did  more  to  advance  the  knowledge  of  insect  life  than 


0  BIOLOGY    AND    ITS    MAKERS 

Lyonet's  researches.  Roesel,  in  Germany,  Reaumur,  in 
France,  and  De  Geer,  in  Sweden,  were  all  distinguished  ob- 
servers in  this  line.  Their  works  are  voluminous  and  are 
well  illustrated.  Those  of  Reaumur  and  De  Geer  took  the 
current  French  title  of  Memoires  pour  servir  a  VHistoire  des 
Insectes.  The  plates  with  which  the  collected  publications 
of  each  of  the  three  men  are  provided  show  many  sketches 
of  external  form  and  details  of  external  anatomy,  but  very 
few  illustrations  of  internal  anatomy  occur.  The  sketches 
of  Roesel  in  particular  are  worthy  of  examination  at  the  pres- 
ent time.  Some  of  his  masterly  figures  in  color  are  fine 
examples  of  the  art  of  painting  in  miniature.  The  name  of 
Roesel  (Fig.  28)  is  connected  also  with  the  earliest  observa- 
tions of  protoplasm  and  with  a  notable  publication  on  the 
Batrachians. 

Reaumur  (Fig.  29),  who  was  distinguished  for  kindly 
and  amiable  personal  qualities,  was  also  an  important  man 
in  his  influence  upon  the  progress  of  science.  He  was  both 
physician  and  naturalist;  he  made  experiments  upon  the 
physiology  of  digestion,  which  aided  in  the  understanding  of 
that  process;  he  invented  the  thermometer  which  bears  his 
name,  and  did  other  services  for  the  advancement  of  sci- 
ence. 

Straus-Durckheim's  Monograph  on  Insect  Anatomy. — 
Insect  anatomy  continued  to  attract  a  number  of  observers, 
but  we  must  go  forward  into  the  nineteenth  century  before 
we  find  the  subject  taking  a  new  direction  and  merging  into 
its  modem  phase.  The  remarkable  monograph  of  Straus- 
Durckheim  represents  the  next  step  in  the  development  of 
insect  anatomy  toward  the  position  that  it  occupies  to-day. 
His  aim  is  clearly  indicated  in  the  opening  sentence  of  his 
preface:  "Having  been  for  a  long  time  occupied  with  the 
study  of  articulated  animals,  I  propose  to  publish  a  general 
work  upon  the  comparative  anatomy  of  that  branch  of  the 


\i:(;i\ST  lOHAKN 

tjr^f^'A  ^iurti  4.vi  yLrz  rji 


M.alilen 


Fig.  28. — RoESEL  von  Rosenhof,   1705-1759- 


98 


BIOLOGY    AND    ITS    MAKERS 


animal  kingdom."  He  was  working  under  the  influence  of 
Cuvier,  who,  some  years  earlier,  had  founded  the  science  of 
comparative  anatomy  and  whom  he  recognized  as  his  great 
exemplar.     His  work  is  dedicated  to  Cuvier,  and  is  accom- 


IG      29. 


-Reaumur,   1683-1757. 


panied  by  a  letter  to  that  great  anatomist  expressing  his 
thanks  for  encouragement  and  assistance. 

Straus-Diirckheim  (i  790-1865)  intended  that  the  general 
considerations  should  be  the  chief  feature  of  his  monograph, 
but  they  failed  in  this  particular  because,  with  the  further 
developments  in  anatomy,  including  embryology  and  the 
cell-theory,  his  general  discussions  regarding  the  articulated 


PROGRESS    OF    MINUTE    ANATOMY  99 

animals  became  obsolete.  The  chief  value  of  his  work  now 
lies  in  what  he  considered  its  secondary  feature,  viz.,  that  of 
the  detailed  anatomy  of  the  cockchafer,  one  of  the  common 
beetles  of  Europe.  Owing  to  changed  conditions,  therefore, 
it  takes  rank  with  the  work  of  Malpighi  and  Lyonet,  as  a 
monograph  on  a  single  form.  Originally  he  had  intended 
to  publish  a  series  of  monographs  on  the  structure  of  insects 
typical  of  the  different  families,  but  that  upon  the  cockchafer 
was  the  only  one  completed. 

Comparison  with  the  Sketches  of  Lyonet. — The  quality 
of  this  work  upon  the  anatomy  of  the  cockchafer  was  excel- 
lent, and  in  1824  it  was  accepted  and  crowned  by  the  Royal 
Institute  of  France.  The  finely  lithographed  plates  were 
prepared  at  the  expense  of  the  Institute,  and  the  book  was 
published  in  1828  with  the  following  cumbersome  title:  Con- 
sider alions  Generales  stir  PAnatomie  com  par  ee  des  Animaux 
Articules  auxquelles  on  a  joint  VAnatomie  Descriptive  du 
Melolontha  Vulgaris  (Hanneton)  donnee  comme  example  de 
r Organisation  des  C ol copter es.  The  109  sketches  with  which 
the  plates  are  adorned  are  very  beautiful,  but  one  who  com- 
pares his  drawings,  figure  by  figure,  with  those  of  Lyonet 
can  not  fail  to  see  that  those  of  the  latter  are  more  detailed 
and  represent  a  more  careful  dissection.  One  illustration 
from  Straus-Diirckheim  will  suffice  to  bring  the  achievements 
of  the  two  men  into  comparison. 

Fig.  30  shows  his  sketch  of  the  anatomy  of  the  central 
nervous  system.  He  undertakes  to  show  only  the  main 
branches  of  the  nerves  going  to  the  different  segments  of  the 
body,  while  Lyonet  brings  to  view  the  distribution  of  the 
minute  terminals  to  particular  muscles.  Comparison  of  other 
figures — notably  that  of  the  dissection  of  the  head— will 
bring  out  the  same  point,  viz.,  that  Lyonet  was  more  detailed 
than  Straus-Diirckheim  in  his  explorations  of  the  anatomy  of 
insects,  and  fully  as  accurate  in  drawing  what  he  had  seen. 


lOO  BIOLOGY   AND    ITS   MAKERS 

Nevertheless,  the  work  of  Straus-Durckheim  is  conceived 
in  a  different  spirit,  and  is  the  first  serious  attempt  to  make 
insect  anatomy  broadly  comparative. 

Comment. — Such  researches  as  those  of  Swammerdam, 
Lyonet,  and  Straus-Durckheim  represent  a  phase  in  the 
progress  of  the  study  of  nature.  Perhaps  their  chief  value 
lies  in  the  fact  that  they  embody  the  idea  of  critical  observa- 
tion. As  examples  of  faithful,  accurate  observations  the  re- 
searches helped  to  bring  about  that  close  study  which  is  our 
only  means  of  getting  at  basal  facts.  These  men  were  all 
enlisted  in  the  crusade  against  superficial  observation.  This 
had  to  have  its  beginning,  and  v/hen  we  witness  it  in  its  early 
stages,  before  the  researches  have  become  illuminated  by  great 
ideas,  the  prodigious  effort  involved  in  the  detailed  researches 
may  seem  to  be  poorly  expended  labor.  Nevertheless,  though 
the  writings  of  these  pioneers  have  become  obsolete,  their 
work  was  of  importance  in  helping  to  lift  observations  upon 
nature  to  a  higher  level. 

Dufour. — Leon  Dufour  extended  the  work  of  Straus- 
Diirckheim  by  publishing,  between  1831  and  1834,  researches 
upon  the  anatomy  and  physiology  of  different  families  of 
insects.  His  aim  was  to  found  a  general  science  of  insect 
anatomy.  That  he  was  unsuccessful  in  accomplishing  this 
was  owing  partly  to  the  absence  of  embryology  and  histology 
from  his  method  of  study. 

Newport. — The  thing  most  needed  now  was  not  greater 
devotion  to  details  and  a  willingness  to  work,  but  a  broaden- 
ing of  the  horizon  of  ideas.  This  arrived  in  the  Englisliman 
Newport,  who  was  remarkable  not  only  for  his  skill  as  a 
dissector,  but  for  his  recognition  of  the  importance  of  embry- 
ology in  elucidating  the  problems  of  structure.  His  article 
"Insecta"  in  Todd's  Cyclopcedia  of  Anatomy  and  Physiol- 
ogy^ in  1 84 1,  and  his  papers  in  the  Philosophical  Transac- 
tions of  the  Royal  Society  contain  tliis  new  kind  of  research. 


Fig.  30. — Nervous    System    of    the    Cockchafer.     (From    Straus- 
Diirckheim's  Monograph,   1828.) 


102  BIOLOGY   AND    ITS    MAKERS 

Von  Baer  had  founded  embryology  by  his  great  work  on  the 
development  of  animals  in  1828,  before  the  investigations  of 
Dufour,  but  it  was  reserved  for  Newport  to  recognize  its 
great  importance  and  to  apply  it  to  insect  anatomy.  He  saw 
clearly  that,  in  order  to  comprehend  his  problems,  the  anat- 
omist must  take  into  account  the  process  of  building  the  body, 
as  well  as  the  completed  architecture  of  the  adult.  The  in- 
troduction of  this  important  idea  made  his  achievement  a 
distinct  advance  beyond  that  of  his  predecessors. 

Leydig. — Just  as  Newport  was  publishing  his  conclusions 
the  cell-theory  was  established  (in  1838-39);  and  this  was 
destined  to  furnish  the  basis  for  a  new  advance.  The  in- 
fluence of  the  doctrine  that  all  tissues  are  composed  of  similar 
vital  units,  called  cells,  was  far-reaching.  Investigators  began 
to  apply  the  idea  in  all  directions,  and  there  resulted  a  new 
department  of  anatomy,  called  histology.  The  subject  of 
insect  histology  was  an  unworked  field,  but  manifestly  one 
of  importance.  Franz  Leydig  (for  portrait  see  p.  175) 
entered  the  new  territory  with  enthusiasm,  and  through  his 
extensive  investigations  all  structural  studies  upon  insects 
assumed  a  nev/  aspect.  In  1864  appeared  his  Vom  Bau  des 
Thierchen  Korpers,  which,  together  with  his  special  articles, 
created  a  new  kind  of  insect  anatomy  based  upon  the  micro- 
scopic study  of  tissues.  The  application  of  this  method  of 
investigation  is  easy  to  see;  just  as  it  is  impossible  to  under- 
stand the  working  of  a  machine  without  a  knowledge  of  its 
construction,  so  a  knowledge  of  the  working  units  of  an  organ 
is  necessary  to  comprehend  its  action.  For  illustration,  it  is 
perfectly  evident  that  we  can  not  understand  what  is  taking 
place  in  an  organ  for  receiving  sensory  impressions  without 
first  understanding  its  mechanism  and  the  nature  of  the 
connections  between  it  and  the  central  part  of  the  nervous 
system.  The  sensory  organ  is  on  the  surface  in  order  more 
readily  to  receive  impressions  from  the  outside  world.     The 


PROGRESS    OF    MINUTE    ANATOMY  103 

sensory  cells  are  also  modifications  of  surface  cells,  and,  as 
a  preliminary  step  to  understanding  their  particular  office, 
we  must  know  the  line  along  which  they  have  become  modi- 
fied to  fit  them  to  receive  stimulation. 

Then,  if  we  attempt  to  follow  in  the  imagination  the  way 
by  which  the  surface  stimulations  reach  the  central  nervous 
system  and  affect  it,  we  must  investigate  all  the  connections. 
It  thus  appears  that  we  must  know  the  intimate  structure  of 
an  organ  in  order  to  understand  its  physiology.  Leydig 
supplied  this  kind  of  information  for  many  organs  of  insects. 
In  his  investigations  we  see  the  foundation  of  that  delicate 
work  upon  the  microscopic  structure  of  insects  which  is  still 
going  forward. 

Summary. — In  this  brief  sketch  we  have  seen  that  the 
study  of  insect  anatomy,  beginning  with  that  of  Malpighi 
and  Swammerdam,  was  lifted  to  a  plane  of  greater  exactitude 
by  Lyonet  and  Straus-Diirckheim.  It  was  further  broadened 
by  the  researches  of  Dufour,  and  began  to  take  on  its  modem 
aspects,  first,  through  the  labors  of  Newport,  who  introduced 
embryology  as  a  feature  of  investigation,  and,  finally,  through 
Leydig's  step  in  introducing  histology.  In  the  combination 
of  the  work  of  these  two  observers,  the  subject  for  the  first 
time  reached  its  proper  position. 

The  studies  of  minute  structure  in  the  seventeenth  and 
eighteenth  centuries  were  by  no  means  confined  to  insects; 
investigations  were  made  upon  a  number  of  other  forms. 
Trembley,  in  the  time  of  Lyonet,  produced  his  noteworthy 
memoirs  upon  the  small  fresh-water  hydra  (Memoires  pour 
servir  a  Vhistoire  des  polypes  d'eau  douce,  1744);  the  illustra- 
tions for  which,  as  already  stated,  were  prepared  by  Lyonet. 
The  structure  of  snails  and  other  mollusks,  of  tadpoles,  frogs, 
and  other  batrachia,  was  also  investigated.  We  have  seen 
that  Swammerdam,  in  the  seventeenth  century,  had  begun 
observations  upon  the  anatomy  of  tadpoles,  frogs,  and  snails, 


I04  BIOLOGY   AND    ITS    MAKERS 

and  also  upon  the  minute  Crustacea  commonly  called  water- 
fleas,  which  are  just  large  enough  to  be  distinguished  by  the 
unaided  eye.  We  should  remember  also  that  in  the  same 
period  the  microscopic  structure  of  plants  began  to  be  inves- 
tigated, notably  by  Grew,  Malpighi,  and  Leeuwenhoek  (see 
Chapter  IV). 

In  addition  to  those  essays  into  minute  anatomy,  in  which 
scalpel  and  scissors  were  employed,  an  endeavor  of  more 
subtle  difficulty  made  its  appeal ;  there  were  forms  of  animal 
life  of  still  smaller  size  and  simpler  organization  that  began 
to  engage  the  attention  of  microscopists.  A  brief  account  of 
the  discovery  and  subsequent  observation  of  these  micro- 
scopic animalcula  will  now  occupy  our  attention. 

The  Discovery  of  the  Simplest  Animals  and  the  Prog- 
ress OF  Observations  upon  Them 

These  single-celled  animals,  since  1845  called  protozoa,, 
have  become  of  unusual  interest  to  biologists,  because  in  them 
the  processes  of  life  are  reduced  to  their  sim.pl est  expression. 
The  vital  activities  taking  place  in  the  bodies  of  higher  animals, 
are  too  complicated  and  too  intricately  mixed  to  admit  of 
clear  analysis,  and,  long  ago,  physiologists  learned  that  the 
quest  for  explanations  of  living  activities  lay  along  the  line 
of  investigating  them  in  their  most  rudimentary  expression. 
The  practical  recognition  of  this  is  seen  in  our  recent  text- 
books upon  human  physiology,  which  commonly  begin  with 
discussions  of  the  life  of  these  simplest  organisms.  That 
greatest  of  all  text-books  on  general  physiology,  written  by 
Max  Verworn,  is  devoted  largely  to  experimental  studies 
upon  these  simple  organisms  as  containing  the  key  to  the 
similar  activities  (carried  on  in  a  higher  degree)  in  higher 
animals.  This  group  of  animals  is  so  important  as  a  field 
of  experimental  observation  that  a  brief  account  of  their 


DISCOVERY    OF   THE    PROTOZOA  105 

discovery  and  the  progress  of  knowledge  in  reference  to  them 
will  be  in  place  in  this  chapter. 

Discovery  of  the  Protozoa. — Leeuw^enhoek  left  so  little 
unnoticed  in  the  microscopic  world  that  we  are  prepared  to 
find  that  he  made  the  first  recorded  observations  upon  these 
animalcula.  His  earliest  observations  were  communicated 
by  letter  to  the  Royal  Society  of  London,  and  were  published 
in  their  Transactions  in  167 7.  It  is  very  interesting  to  read 
his  descriptions  expressed  in  the  archaic  language  of  the  time. 
The  following  quotation  from  a  Dutcli  letter  turned  into 
English  will  suffice  to  give  the  flavor  of  his  writing: 

"In  the  year  1675  I  discovered  living  creatures  in  rain- 
water which  had  stood  but  four  days  in  a  new  earthen  pot, 
glazed  blew  within.  This  invited  me  to  view  the  water  with 
great  attention,  especially  those  little  animals  appearing  to 
me  ten  thousand  times  less  than  those  represented  by  Mons. 
Swammerdam,  and  by  him  called  water-fleas  or  water-lice, 
which  may  be  perceived  in  the  water  with  the  naked  eye. 
The  first  sorte  by  me  discovered  in  the  said  water,  I  divers 
times  observ^ed  to  consist  of  five,  six,  seven  or  eight  clear 
globules,  without  being  able  to  discover  any  film  that  held 
them  together  or  contained  them.  When  these  animalcula, 
or  living  atoms,  did  move  they  put  forth  two  little  horns, 
continually  moving  themselves;  the  place  between  these 
two  horns  was  flat,  though  the  rest  of  the  body  was  roundish, 
sharpening  a  little  towards  the  end,  where  they  had  a  tayle, 
near  four  times  the  length  of  the  whole  body,  of  the  thick- 
ness (by  my  microscope)  of  a  spider's  web;  at  the  end  of 
which  appeared  a  globule,  of  the  bigness  of  one  of  those 
which  made  up  the  body;  which  tayle  I  could  not  perceive 
even  in  very  clear  water  to  be  mov'd  by  them.  These  little 
creatures,  if  they  chanced  to  light  upon  the  least  filament 
or  string,  or  other  such  particle,  of  which  there  are  many  in 
the  water,  especially  after  it  has  stood  some  days,  they  stook 


I06  BIOLOGY   AND    ITS    MAKERS 

entangled  therein,  extending  their  body  in  a  long  round,  and 
striving  to  dis-entangle  their  tayle;  whereby  it  came  to  pass, 
that  their  whole  body  lept  back  towards  the  globule  of  the 
tayle,  which  then  rolled  together  serpent-like,  and  after  the 
manner  of  copper  or  iron  wire,  that  having  been  wound 
around  a  stick,  and  unwound  again,  retains  those  v/indings 
and  turnings,"  etc.* 

x\ny  one  who  has  examined  under  the  microscope  the  well- 
known  bell -animalcule  will  recognize  in  this  first  description 
of  it,  the  stalk,  and  its  form  after  contraction  under  the  desig- 
nation of  a  '  tayle  which  retains  those  windings  and  turnings.' 

There  are  many  other  descriptions,  but  the  one  given  is 
typical  of  the  others.  He  found  the  little  animals  in  water, 
in  infusions  of  pepper,  and  other  vegetable  substances,  and 
on  that  account  they  came  soon  to  be  designated  infusoria. 
His  observations  were  not  at  first  accompanied  by  sketches, 
but  in  1 71 1  he  sent  some  drawings  with  further  descriptions. 

O.  Fr.  Mtiller. — These  animalcula  became  favorite  ob- 
jects of  microscopic  study.  Descriptions  began  to  accu- 
mulate and  drawings  to  be  made  until  it  became  evident  that 
there  were  many  different  kinds.  It  was,  however,  more 
than  one  hundred  years  after  their  discovery  by  Leeuwenhoek 
that  the  first  standard  work  devoted  exclusively  to  these 
animalcula  was  published.  This  treatise  by  O.  Fr.  Miiller 
was  published  in  1786  under  the  title  of  Animalctda  Infusoria, 
The  circumstance  that  this  volume  of  quarto  size  had  367 
pages  of  description  with  50  plates  of  sketches  will  gi^'e  some 
indication  of  the  number  of  protozoa  known  at  that  time. 

Ehrenberg. — Observations  in  this  domain  kept  accu- 
mulating, but  the  next  publication  necessary  to  mention  is  that 
of  Ehrenberg  (i  795-1876).  This  scientific  traveler  and 
eminent  observer  was  the  author  of  several  works.     He  was 

*  Kent's  Manual  of  the  Infusoria,  Vol.  I,  p.  3.     Quotation   from  the 
Philosophical  Transactions  for  the  year  1677. 


DISCOVERY    OF   THE    PROTOZOA  1^7 

one  of  the  early  observers  of  nerve  fibres  and  of  many  other 
structures  of  the  animal  frame.  His  book  of  the  protozoa 
is  a  beautifully  illustrated  monograph  consisting  of  532  pages 
of  letterpress  and  69  plates  of  folio  size.  It  was  published  in 
1836  under  the  German  title  of  Die  Injusionsthierchen  als 
Vollkommene  Or ganismen,  or  ''The  Infusoria  as  Perfect  Or- 
ganisms." The  animalcula  which  he  so  faithfully  represented 
in  his  sketches  have  the  habit,  when  feeding,  of  taking  into 
the  body  collections  of  food -particles,  aggregated  into  spher- 
ical globules  or  food  vacuoles.  These  are  distinctly  sepa- 
rated, and  slowly  circulate  around  the  single-celled  body  while 
they  are  undergoing  digestion.  In  a  fully  fed  animal  these 
food-vacuoles  occupy  different  positions,  and  are  enclosed  in 
globular  spaces  in  the  protoplasm,  an  adjustment  that  gave 
Ehrenberg  the  notion  that  the  animals  possessed  many 
stomachs.  Accordingly  he  gave  to  them  the  name  ''  Poly- 
gastrica,"  and  assigned  to  them  a  much  higher  grade  of 
organization  than  they  really  possess.  These  conclusions, 
based  on  the  general  arrangement  of  food  globules,  seem 
very  curious  to  us  to-day.  His  publication  was  almost  simul- 
taneous with  the  announcement  of  the  cell-theory  (1838-39), 
the  acceptance  of  which  was  destined  to  overthrow  his  con- 
ception of  the  protozoa,  and  to  make  it  clear  that  tissues  and 
organs  can  belong  only  to  multicellular  organisms. 

Ehrenberg  (Fig.  31)  was  a  man  of  great  scientific  attain- 
ments, and  notwithstanding  the  grotesqueness  of  some  of  his 
conclusions,  was  held  in  high  esteem  as  a  scientific  investi- 
gator. His  observations  were  accurate,  and  the  beautiful 
figures  vvith  which  his  work  on  the  protozoa  is  embellished 
were  executed  with  such  fidelity  regarding  fine  points  of 
microscopic  detail  that  they  are  of  value  to-day. 

Dujardin,  whom  we  shall  soon  come  to  know  as  the  dis- 
coverer of  protoplasm,  successfully  combated  the  concUisions 
of  Ehrenberg  regarding  the  organization  of  the  protozoa. 


io8 


BIOLOGY   AND    ITS    MAKERS 


For  a  time  the  great  German  scientist  tried  to  maintain  his 
point,  that  the  infusoria  have  many  stomachs,  but  this  was 
completely  swept  away,  and  finally  the  contention  of  Von 
Siebold  was  adopted  to  the  effect  that  these  animals  are  each 
composed  of  a  single  cell. 

In  1845  Stein,  whose  influence  was  greater  than  that  of 
Ehrenberg,  is  engrossed  in  proposing  names  for  the  suborders 


Fig.  31. — Ehrenberg,   1795-1876. 


of  infusoria  based  upon  the  distribution  of  cilia  upon  their 
bodies.  This  simple  method  of  classification,  as  well  as  the 
names  introduced  by  Stein,  is  still  in  use. 

Since  Stein  there  have  been  many  workers  on  protozoa, 
but  the  researches  of  Richard  Hertwig,  Biitschli,  Doeflein, 
and  Fritz  Schaudinn  are  of  especial  importance,  and  with  the 


DISCOVERY  OF  THE   PROTOZOA  109 

contributions  of  these  and  other  observers  we  enter  the 
modern  epoch. 

The  importance  of  these  animals  in  affording  a  field  for 
experimentation  on  the  simplest  expressions  of  life  has  al- 
ready been  indicated.  Many  interesting  problems  have 
arisen  in  connection  with  recent  studies  of  them  and,  as  a 
consequence,  a  separate  division  of  biological  study  desig- 
nated protozoology  is  recognized.  The  group  embraces  the 
very  simplest  manifestations  of  animal  Hfe,  and  the  experi- 
ments upon  the  different  forms  light  the  way  for  studies 
of  the  vital  activities  of  the  higher  animals.  Some  of  the 
protozoa  are  disease  producing;  as  the  microbe  of  malaria, 
of  the  sleeping  sickness,  etc.,  while,  as  is  well  known,  most 
diseases  that  have  been  traced  to  specific  germs  are  caused 
by  plants — the  bacteria.  Many  experiments  of  Maupas, 
Calkins  and  others  have  a  bearing  upon  the  discussions 
regarding  the  immortality  of  the  protozoa,  an  idea  which 
was  at  one  time  a  feature  of  Weissmann's  theory  of  heredity. 
Binet  and  others  have  discussed  the  evidences  of  psychic 
life  in  these  micro-organisms,  and  the  daily  activity  of  a 
protozoan  became  the  field  for  observation  and  record  in 
an  American  laboratory  of  psychology.  The  extensive  stud- 
ies of  Jennings  on  the  nature  of  their  responses  to  stim- 
ulations form  a  basis  for  some  of  the  discussions  on  animal 
behavior. 


CHAPTER    VI 

LINN^US  AND  SCIENTIFIC  NATURAL  HISTORY 

We  turn  now  from  the  purely  anatomical  side  to  consider 
the  parallel  development  of  the  classification  of  animals  and 
of  plants.  Descriptive  natural  history  reached  a  very  low 
level  in  the  early  Christian  centuries,  and  remained  there 
throughout  the  Middle  Ages.  The  return  to  the  writings  of 
Aristotle  was  the  first  influence  tending  to  lift  it  to  the  position 
from  which  it  had  fallen.  After  the  decline  of  ancient  civili- 
zation there  was  a  period  in  which  the  writers  of  classical 
antiquity  were  not  read.  Not  only  were  the  v/ritings  of  the 
ancient  philosophers  neglected,  but  so  also  were  those  of  the 
literary  men  as  well,  the  poets,  the  story-tellers,  and  the  his- 
torians. As  related  in  Chapter  I,  there  were  no  observations 
of  animated  nature,  and  the  growing  tendency  of  the  educated 
classes  to  envelop  themselves  in  metaphysical  speculations 
was  a  feature  of  intellectual  life. 

The  Physiologus  or  Sacred  Natural  History. — During  this 
period  of  crude  fancy,  with  a  fog  of  mysticism  obscuring  all 
phenomena  of  nature,  there  existed  a  peculiar  kind  of  natural 
history  that  was  produced  under  theological  influence.  The 
manuscripts  in  which  this  sacred  natural  history  v/as  em- 
bodied exist  in  various  forms  and  in  about  a  dozen  languages 
of  Eastern  and  Western  Europe.  The  writings  are  known 
under  the  general  title  of  the  Physiologus,  or  the  Bestiarius. 
This  served  for  nearly  a  thousand  years  as  the  principal 
source  of  thought  regarding  natural  history.     It  contains 

no 


LINN^US    AND    NATURAL   HISTORY  m 

accounts  of  animals  mentioned  in  the  Bible  and  others  of  a 
purely  mythical  character.  These  are  made  to  be  symbolical 
of  religious  beliefs,  and  are  often  accompanied  by  quotations 
of  texts  and  by  moral  reflections.  The  phoenix  rising  from 
its  ashes  typifies  the  resurrection  of  Christ.  In  reference  to 
young  lions,  the  Physiologus  says:  "The  lioness  giveth  birth 
to  cubs  which  remain  three  days  without  life.  Then  cometh 
the  lion,  breath eth  upon  them,  and  bringeth  them  to  life.  .  .  . 
Thus  it  is  that  Jesus  Christ  during  three  days  was  deprived 
of  life,  but  God  the  Father  raised  him  gloriously."  (Quoted 
from  White,  p.  35.)  Besides  forty  or  fifty  common  animals, 
the  unicorn  and  the  dragon  of  the  Scriptures,  and  the  fabled 
basilisk  and  phoenix  of  secular  writings  are  described,  and 
morals  are  drawn  from  the  stories  about  them.  Some  of  the 
accounts  of  animals,  as  the  lion,  the  panther,  the  serpent,  the 
weasel,  etc.,  etc.,  are  so  curious  that,  if  space  permitted,  it 
would  be  interesting  to  quote  them;  but  that  would  keep  us 
too  long  from  following  the  rise  of  scientific  natural  history 
from  this  basis. 

For  a  long  time  the  religious  character  of  the  contempla- 
tions of  nature  was  emphasized  and  the  prevalence  of  theo- 
logical influence  in  natural  history  is  shown  in  various  titles, 
as  Lesser's  Theology  oj  Insects,  Swammerdam's  Bihlia 
NaturcB,  Spallanzani's  Tracts,  etc. 

The  zoology  of  the  Physiologus  w^as  of  a  much  lower  grade 
than  any  we  know  about  among  the  ancients,  and  it  is  a 
curious  fact  that  progress  was  made  by  returning  to  the 
natural  history  of  fifteen  centuries  in  the  past.  The  transla- 
tion of  Aristotle's  writings  upon  animals,  and  the  disposition 
to  read  them,  mark  this  advance.  When,  in  the  Middle 
Ages,  the  boundaries  of  interest  began  to  be  extended,  it 
came  like  an  entirely  new  discovery,  to  find  in  the  writings 
of  the  ancients  a  storehouse  of  philosophic  thought  and  a 
higher  grade  of  learning   than   that   of   the   period.     The 


112  BIOLOGY    AND    ITS    MAKERS 

translation  and  recopying  of  the  writers  of  classical  antiquity 
was,  therefore,  an  important  step  in  the  revival  of  learning. 
These  writings  were  so  much  above  the  thought  of  the  time 
that  the  belief  was  naturally  created  that  the  ancients  had 
digested  all  learning,  and  they  were  pointed  to  as  unfailing 
authorities  in  matters  of  science. 

The  Return  to  the  Science  of  the  Ancients. — The  return  to 
Aristotle  was  wholesome,  and  under  its  influence  men  turned 
their  attention  once  more  to  real  animals.  Comments  upon 
Aristotle  began  to  be  made,  and  in  course  of  time  independent 
treatises  upon  animals  began  to  appear.  One  of  the  first  to 
modify  Aristotle  to  any  purpose  was  Edward  Wotton,  the 
English  physician,  who  published  in  1552  a  book  on  the  dis- 
tinguishing characteristics  of  animals  {De  Differ entiis  Ani- 
malium).  This  was  a  complete  treatise  on  the  zoology  of 
the  period,  including  an  account  of  the  different  races  of 
mankind.  It  was  beautifully  printed  in  Paris,  and  was 
dedicated  to  Edward  VI.  Although  embracing  ten  books, 
it  was  by  no  means  so  ponderous  as  were  som.e  of  the  treatises 
that  followed  it.  The  work  was  based  upon  Aristotle,  but 
the  author  introduced  new  matter,  and  also  added  the  group 
of  zoophytes,  or  plant-like  animals  of  the  sea. 

Gesner. — The  next  to  reach  a  distinctly  higher  plane  was 
Conrad  Gesner  (i 516-1 565),  the  Swiss,  who  was  a  contem- 
porary of  Vesalius.  He  was  a  practising  physician  who,  in 
1553,  was  made  professor  of  natural  history  in  Zurich.  A 
man  of  extraordinary  talent  and  learning,  he  turned  out  an 
astonishing  quantity  of  work.  Besides  accomplishing  much 
in  scientific  lines,  he  translated  from  Greek,  Arabic,  and 
Hebrew,  and  published  in  twenty  volumes  a  universal  cat- 
alogue of  all  works  known  in  Latin,  Greek,  and  Hebrew, 
either  printed  or  in  manuscript  form.  In  the  domain  of 
natural  history  be  began  to  look  critically  at  animals  with  a 
view  to  describing  them,  and  to  collect  with  zealous  care  new 


LINN^US    AND    NATURAL    HISTORY  113 

observations  upon  their  habits.  His  great  work  on  natural 
history  (Historia  Animalium)  began  to  appear  in  1551,  when 
he  was  thirty-five  years  of  age,  and  four  of  the  five  volumes 
were  published  by  1556.  The  fifth  volume  was  not  pub- 
lished until  1587,  tv/enty-two  years  after  his  death.  The 
complete  work  consists  of  about "  4,500  folio  pages,"  profusely 
illustrated  with  good  figures.  The  edition  which  the  writer 
has  before  him — that  of  1 585-1604 — embraces  3,200  pages 
of  text  and  953  figures. 

Brooks  says:  "One  of  Gesner's  greatest  serv^ices  to  nat- 
ural science  is  the  introduction  of  good  illustrations,  which  he 
gives  his  reader  by  hundreds."  He  was  so  exacting  about 
the  quality  of  his  illustrations  that  his  critical  supervision  of 
the  work  of  artists  and  engravers  had  its  influence  upon  con- 
temporary art.  Some  of  the  best  woodcuts  of  the  period  are 
found  in  his  work.  Albrecht  Diirer  supplied  one  of  the 
originals — the  drawing  of  the  rhinoceros — and  it  is  interest- 
ing to  note  that  it  is  by  no  means  the  best,  a  circumstance 
which  indicates  how  effectively  Gesner  held  his  engravers 
and  draughtsmen  up  to  fine  work.  He  was  also  careful 
to  mold  his  writing  into  graceful  form,  and  this,  combined 
with  the  illustrations,  "  made  science  attractive  without  sac- 
rificing its  dignity,  and  thus  became  a  great  educational 
influence." 

In  preparing  his  work  he  sifted  the  writings  of  about  two 
hundred  and  fifty  authors,  and  while  his  book  is  largely  a 
compilation,  it  is  enriched  with  many  observations  of  his  own. 
His  descriptions  are  verbose,  but  discriminating  in  separating 
facts  and  observations  from  fables  and  speculations.  He 
could  not  entirely  escape  from  old  traditions.  There  are  re- 
tained in  his  book  pictures  of  the  sea-serpent,  the  mermeids, 
and  a  few  other  fanciful  and  grotesque  sketches,  but  for  the 
most  part  the  drawings  are  made  from  the  natural  objects. 
The  descriptions  are  in  several  parts  of  his  work  alphabeti- 


114 


BIOLOGY   AND    ITS    MAKERS 


cally  arranged,  for  convenience  of  reference,  and  thus  ani- 
mals that  were  closely  related  are  often  widely  separated. 

Gesner  (Fig.  32)  sacrificed  his  life  to  professional  zeal 
during  the  prevalence  of  the  plague  in  Zurich  in  1 564.  Hav- 
ing greatly  overworked  in  the  care  of  the  sick,  he  was  seized 
with  the  disease,  and  died  at  the  age  of  forty-nine. 

Considered  from  the  standpoint  of  descriptions  and  illus- 
trations, Gesner's  Historia  Animalium  remained  for  a  long 


Fig.  32. — Gesner     1516-1565. 


time  the  best  work  in  zoology.  He  was  the  best  zoologist 
between  Aristotle  and  John  Ray,  the  immediate  predecessor 
of  Linnaeus. 

Jonston  and  Aldrovandi. — At  about  the  same  period  as 
Gesner's  work  there  appeared  two  other  voluminous  publica- 
tions, which  are  well  known — those  of  Jonston,  the  Scot 


LINNvEUS    AND    NATURAL    HISTORY  "5 

{Historia  Animalium,  1 549-1 553),  and  Aldrovandi,  the 
Italian  {Opera,  1599-1606).  The  former  consisted  of  four 
foh'o  volumes,  and  the  latter  of  thirteen,  of  ponderous  size, 
to  which  was  added  a  fourteenth  on  plants.  Jonston's  works 
were  translated,  and  were  better  known  in  England  than  those 
of  Gesner  and  Aldrovandi.  The  wood -engravings  in  Aldro- 
vandi's  volume  are  coarser  than  those  of  Gesner,  and  are  by 
no  means  so  lifelike.  In  the  Institute  at  Bologna  are  pre- 
served twenty  volumes  of  figures  of  animals  in  color,  which 
were  the  originals  from  which  the  engravings  were  made. 
These  are  said  to  be  much  superior  to  the  reproductions. 
The  encyclopaedic  nature  of  the  writings  of  Gesner,  Aldro- 
vandi, and  Jonston  has  given  rise  to  the  convenient  and 
expressive  title  of  the  encyclopaedists. 

Ray. — John  Ray,  the  forerunner  of  Linnaeus,  built  upon 
the  foundations  of  Gesner  and  others,  and  raised  the  natural- 
history  edifice  a  tier  higher.  He  greatly  reduced  the  bulk 
of  publications  on  natural  history,  sifting  from  Gesner  and 
Aldrovandi  their  irrelevancies,  and  thereby  giving  a  more 
modern  tone  to  scientific  writings.  He  was  the  son  of  a 
blacksmith,  and  was  born  in  southern  England  in  1628. 
The  original  form  of  the  family  name  was  Wray.  He  was 
graduated  at  the  University  of  Cambridge,  and  became  a 
fellow  of  Trinity  College.  Here  he  formed  a  friendship  with 
Francis  Willughby,  a  young  man  of  wealth  whose  tastes  for 
natural  history  were  like  his  own.  This  association  proved 
a  happy  one  for  both  parties.  Ray  had  taken  orders  in  the 
Church  of  England,  and  held  his  university  position  as  a 
cleric;  but,  from  conscientious  scruples,  he  resigned  his 
fellowship  in  1662.  Thereafter  he  received  financial  assist- 
ance from  Willughby,  and  the  two  men  traveled  extensively 
in  Great  Britain  and  on  the  Continent,  with  the  view  of  inves- 
tigating the  natural  history  of  the  places  that  they  visited. 
On  these  excursions  Willughby  gave  particular  attention  to 


Ii6 


BIOLOGY    AND    ITS    MAKERS 


animals  and  Ray  to  plants.  Of  Ray's  several  publications 
in  botany,  his  Historia  Plantarum  in  three  volumes  (1686- 
1704)  is  the  most  extensive.  In  another  work,  as  early  as 
1682,  he  had  proposed  a  new  classification  of  plants,  which 


Fig.  33. — John  Ray,   1628-1705. 


in  the  next  century  was  adopted  by  Jussieu,  and  which  gives 
Ray  a  place  in  the  history  of  botany. 

Willughby  died  in  1662,  at  the  age  of  thirty-eight,  leaving 
an  annuity  to  Ray,  and  charging  him  with  the  education  of 


LINN^US    AND    NATURAL    HISTORY  H? 

his  two  sons,  and  the  editing  of  his  manuscripts.  Ray  per- 
formed these  duties  as  a  faithful  friend  and  in  a  generous 
spirit.  He  edited  and  puWished  Willughby's  book  on  birds 
(1678)  and  fishes  (1686)  with  important  additions  of  his  ow^n, 
for  which  he  sought  no  credit. 

After  completing  his  tasks  as  the  literary  executor  of  Wil- 
lughby,  he  returned  in  1678  to  his  birthplace  and  continued 
his  studies  in  natural  history.  In  1691  he  published  "The 
Wisdom  of  God  manifested  in  the  Works  of  the  Creation," 
which  was  often  reprinted,  and  became  the  forerunner  of  the 
works  on  natural  theology  like  Paley's,  etc.  This  was  an 
amplification  of  ideas  he  had  embodied  in  a  sermon  thirty- 
one  years  earlier,  and  which  at  that  time  attracted  much 
notice.  He  now  devoted  himself  Largely  to  the  study  of  ani- 
mals, and  in  1693  published  a  w^ork  on  the  quadrupeds  and 
serpents,  a  work  which  gave  him  high  rank  in  the  history  of 
the  classification  of  animals.  He  died  in  1705,  but  he  had 
accomplished  much  good  work,  and  was  not  forgotten.  In 
1844  there  was  founded,  in  London,  in  his  memory,  the  Ray 
Society  for  the  publication  of  rare  books  on  botany  and 
zoology. 

Ray's  Idea  of  Species. — One  of  the  features  of  Ray's 
work,  in  the  light  of  subsequent  development,  is  of  special 
interest,  and  that  is  his  limiting  of  species.  He  was  the  first 
to  introduce  into  natural  history  an  exact  conception  of 
species.  Before  his  time  the  word  had  been  used  in  an 
indefinite  sense  to  embrace  groups  of  greater  or  less  extent, 
but  Ray  applied  it  to  individuals  derived  from  similar  par- 
ents, thus  making  the  term  species  stand  for  a  particular  kind 
of  animal  or  plant.  He  noted  some  variations  among  species, 
and  did  not  assign  to  them  that  unvarying  and  constant  char- 
acter ascribed  to  them  by  Linnaeus  and  his  followers.  Ray 
also  made  use  of  anatomy  as  the  foundation  for  zoological 
classification,  and  introduced  great  precision  and  clearness 


Il8  BIOLOGY   AND    ITS    MAKERS 

into  his  definitions  of  groups  of  animals  and  plants.  In  the 
particulars  indicated  above  he  represents  a  great  advance 
beyond  any  of  his  precursors,  and  marks  the  parting  of  the 
ways  between  mediaeval  and  modem  natural  history. 

In  Germany  Klein  (1685-1759)  elaborated  a  system  of 
classification  embracing  the  entire  animal  kingdom.  His 
studies  were  numerous,  and  his  system  would  have  been  of 
much  wider  influence  in  molding  natural  history  had  it  not 
been  overshadowed  by  that  of  I^innaeus. 

Linnaeus  or  Linne. — The  service  of  Linnaeus  to  natural 
history  was  unique.  The  large  number  of  specimens  of 
animals  and  plants,  ever  increasing  through  the  collections 
of  travelers  and  naturalists,  were  in  a  confused  state,  and 
there  was  great  ambiguity  arising  from  the  lack  of  a  method- 
ical way  of  arranging  and  naming  them.  They  were  known 
by  verbose  descriptions  and  local  names.  No  scheme  had 
as  yet  been  devised  for  securing  uniformity  in  applying  names 
to  them.  The  same  animal  and  plant  had  different  names 
in  the  different  sections  of  a  country,  and  often  different 
plants  and  animals  had  the  same  name.  In  different  coun- 
tries, also,  their  names  were  greatly  diversified.  What  was 
especially  needed  was  some  great  organizing  mind  to  cata- 
logue the  animals  and  plants  in  a  systematic  way,  and  to  give 
to  natural  science  a  common  language.  Linnaeus  possessed 
this  methodizing  mind  and  supplied  the  need.  While  he  did 
little  to  deepen  the  knowledge  of  the  organization  of  animal 
and  plant  life,  he  did  much  to  extend  the  number  of  known 
forms;  he  simplified  the  problem  of  cataloguing  them,  and  he 
invented  a  simple  method  of  naming  them  which  was  adopted 
throughout  the  world.  By  a  happy  stroke  he  gave  to  biology 
a  new  language  that  remains  in  use  to-day.  The  tremendous 
influence  of  this  may  be  realized  when  we  rem^ember  that 
naturalists  everyv/here  use  identical  names  for  the  same 
animals  and  plants.     The  residents  of  Japan,  of  Italy,  of 


LINN^US    AND    NATURAL    HISTORY  II9 

Spain,  of  all  the  world,  in  fact,  as  was  just  said,  employ  the 
same  Latin  names  in  classifying  organic  forms. 

He  also  inspired  many  students  with  a  love  for  natural 
history  and  gave  an  impulse  to  the  advance  of  that  science 
w^iich  was  long  felt.  We  can  not  gainsay  that  a  higher  class 
of  service  has  been  rendered  by  those  of  philosophic  mind 
devoted  to  the  pursuit  of  comparative  anatomy,  but  the  step 
of  Linnaeus  was  a  necessary  one,  and  aided  greatly  in  the 
progress  of  natural  history.  Without  this  step  the  discoveries 
and  observations  of  others  would  not  have  been  so  readily 
understood,  and  had  it  not  been  for  his  organizing  force  all 
natural  science  would  have  been  held  back  for  want  of  a 
common  language.  A  close  scrutiny  of  the  practice  among 
naturalists  in  the  time  of  Linnaeus  shows  that  he  did  not 
actually  invent  the  binomial  nomenclature,  but  by  adopting 
the  suggestions  of  others  he  elaborated  the  system  of  classifi- 
cation and  brought  the  new  language  into  common  use. 

Personal  History. — Leaving  for  the  present  the  system  of 
Linnaeus,  we  shall  give  attention  to  the  personal  history  of 
the  man.  The  great  Swedish  naturalist  was  born  in  Rashult 
in  1 707.  His  father  was  the  pastor  of  the  village,  and  intended 
his  eldest  son,  Carl,  for  the  same  high  calling.  The  original 
family  name  was  Ignomarsen,  but  it  had  been  changed  to  Lin- 
delius,  from  a  tall  linden-tree  growing  in  that  part  of  the  coun- 
try. In  1761  a  patent  of  nobility  was  granted  by  the  crown 
to  Linnaeus,  and  thereafter  he  was  styled  Carl  von  Linne. 

His  father's  resources  were  very  limited,  but  he  man- 
aged to  send  his  son  to  school,  though  it  must  be  confessed 
that  young  Linnaeus  showed  little  liking  for  the  ordinary 
branches  of  instruction.  His  time  was  spent  in  collecting 
natural-history  specimens,  and  his  mind  was  engaged  in 
thinking  about  them.  The  reports  of  his  low  scholarship 
and  the  statement  of  one  of  his  teachers  that  he  showed  no 
aptitude  for  learning  were  so  disappointing  to  his  father  that, 


I20  BIOLOGY   AND    ITS   MAKERS 

in  1726,  he  prepared  to  apprentice  Carl  to  a  shoemaker,  but 
was  prevented  from  doing  so  through  the  encouragement 
of  a  doctor  who,  being  able  to  appreciate  the  quality  of  mind 
possessed  by  the  young  Linnaeus,  advised  allowing  him  to 
study  medicine  instead  of  preparing  for  theology. 

Accordingly,  with  a  sum  amounting  to  about  $40,  all  his 
father  could  spare,  he  set  off  for  the  University  of  Lund,  to 
pursue  the  study  of  medicine.  He  soon  transferred  to  the 
University  of  Upsala,  where  the  advantages  were  greater.  His 
poverty  placed  himunder  thegreatest  straits  for  the  necessities 
of  life,  and  he  enjoyed  no  luxuries.  While  in  the  university 
he  mended  his  shoes,  and  the  shoes  which  were  given  to  him 
by  some  of  his  companions,  with  paper  and  birch-bark,  to 
keep  his  feet  from  the  damp  earth.  But  his  means  did  not 
permit  of  his  taking  his  degree  at  Upsala,  and  it  was  not  until 
eight  years  later,  in  1735,  that  he  received  his  degree  in  Holland. 

At  Upsala  he  was  relieved  from  his  extreme  poverty  by 
obtaining  an  assistant's  position,  and  so  great  was  his  knowl- 
edge of  plants  that  he  was  delegated  to  read  the  lectures  of 
the  aged  professor  of  botany,  Rudbeck. 

In  1732  he  was  chosen  by  the  Royal  Society  of  Upsala  to 
visit  Lapland  as  a  collector  and  observer,  and  left  the  univer- 
sity without  his  degree.  On  returning  to  Upsala,  his  lack 
of  funds  made  itself  again  painfully  felt,  and  he  undertook 
to  support  himself  by  giving  public  lectures  on  botany,  chem- 
istry, and  mineralogy.  He  secured  hearers,  but  the  con- 
tinuance of  his  lectures  was  prevented  by  one  of  his  rivals  on 
the  ground  that  Linnaeus  had  no  degree,  and  was  therefore 
legally  disqualified  from  taking  pay  for  instruction.  Pres- 
ently he  became  tutor  and  traveling  companion  of  a  wealthy 
baron,  the  governor  of  the  province  of  Dalecarlia,  but  this 
employment  was  temporary. 

Helped  by  His  Fiancee. — His  friends  advised  him  to 
secure  his  medical  degree  and  settle  as  a  practitioner.     Al- 


LINN^US    AND    NATURAL    HISTORY  121 

though  he  lacked  the  necessarv  funds,  one  circumstance  con- 
tributed to  bring  about  this  end:  he  had  formed  an  attach- 
ment for  the  daughter  of  a  weahhy  physician,  named  More 
or  Moraeus,  and  on  applying  for  her  hand  in  marriage,  her 
father  made  it  a  condition  of  his  consent  that  Linnaeus  should 
take  his  medical  degree  and  establish  himself  in  the  practice 
of  medicine.  The  young  lady,  who  was  thrifty  as  well  as 
handsome,  offered  her  savings,  amounting  to  one  hundred 
dollars  (Swedish),  to  her  lover.  He  succeeded  in  adding  to 
this  sum  by  his  own  exertions,  and  with  thirty-six  Swedish 
ducats  set  off  for  Holland  to  qualify  for  his  degree.  He  had 
practically  met  the  requirements  for  the  medical  degree  by 
his  previous  studies,  and  after  a  month's  residence  at  the 
University  of  Hardewyk,  his  thesis  was  accepted  and  he  was 
granted  the  degree  in  June,  1735,  in  the  twenty-eighth  year 
of  his  age. 

Instead  of  returning  at  once  to  Sweden,  he  went  to 
Leyden,  and  made  the  acquaintance  of  several  well-known 
scientific  men.  He  continued  his  botanical  studies  with  great 
energy,  and  now  began  to  reap  the  benefits  of  his  earlier 
devotion  to  natural  history.  His  heart-breaking  and  harass- 
ing struggles  were  now  over. 

The  Systema  Naturae. — He  had  in  his  possession  the 
manuscript  of  his  Systema  NaturcF,  and  with  the  encourage- 
ment of  his  new  friends  it  was  published  in  the  same  year. 
The  first  edition  (1735)  of  that  notable  work,  which  was 
afterward  to  bring  him  so  much  fame,  consisted  of  twelve 
printed  folio  pages.  It  was  merely  an  outline  of  the  arrange- 
ments of  plants,  animals,  and  minerals  in  a  methodical  cat- 
alogue. This  work  passed  through  twelve  editions  during 
his  lifetime,  the  last  one  appearing  in  1768.  After  the  first 
edition,  the  books  were  printed  in  octavo  form,  and  in  the 
later  editions  were  greatly  enlarged.  A  copy  of  the  first 
edition  was  sent  to  Boerhaave,  the  most  distinguished  pro- 


122  BIOLOGY   AND    ITS    MAKERS 

fessor  in  the  University  of  Leyden,  and  secured  for  Linnaeus 
an  interview  with  that  distinguished  physician,  who  treated 
him  with  consideration  and  encouraged  him  in  his  work. 
Boerhaave  was  already  old,  and  had  not  long  to  live;  and 
when  Linnaeus  was  about  to  leave  Holland  in  1738,  he  ad- 
mitted him  to  his  sick-chamber  and  bade  him  a  most  affec- 
tionate adieu,  and  encouraged  him  to  further  work  by  most 
kindly  and  appreciative  expressions. 

Through  the  influence  of  Boerhaave,  Linnaeus  became  the 
medical  attendant  of  Cliffort,  the  burgomaster  at  Amsterdam, 
who  had  a  large  botanic  garden.  Cliffort,  being  desirous  of 
extending  his  collections,  sent  Linnaeus  to  England,  where 
he  met  Sir  Hans  Sloane  and  other  eminent  scientific  men  of 
Great  Britain.  After  a  short  period  he  returned  to  Holland, 
and  in  1 737  brought  out  the  Genera  Plantarum,  a  very  original 
work,  containing  an  analysis  of  all  the  genera  of  plants.  He 
had  previously  published,  besides  the  Sy sterna  Naturce,  his 
Fundamenta  Botanica,  1735,  and  Bibliotheca  Boianica,  1736, 
and  these  works  served  to  spread  his  fame  as  a  botanist 
throughout  Europe. 

His  Wide  Recognition. — ^An  illustration  of  his  wide  rec- 
ognition is  afforded  by  an  anecdote  of  his  first  visit  to  Paris 
in  1738.  "On  his  arrival  he  went  first  to  the  Garden  of 
Plants,  where  Bernard  de  Jussieu  was  describing  some 
exotics  in  Latin.  He  entered  w^ithout  opportunity  to  intro- 
duce himself.  There  was  one  plant  which  the  demonstrator 
had  not  yet  determined,  and  which  seemed  to  puzzle  him. 
The  Swede  looked  on  in  silence,  but  observing  the  hesitation 
of  the  learned  professor,  cried  out  'Hcec  planta  jaciem  Ame- 
ricanam  habet.^  '  It  has  the  appearance  of  an  American  plant.' 
Jussieu,  surprised,  turned  about  quickly  and  exclaimed  'You 
are  Linnaeus.'  'I  am,  sir,'  was  the  reply.  The  lecture  was 
stopped,  and  Bernard  gave  the  learned  stranger  an  affec- 
tionate welcome." 


LINN^US    AND    NATURAL    HISTORY  I23 

Return  to  Sweden. — After  an  absence  of  three  and  one- 
half  years,  Linnaeus  returned  to  his  native  country  in  1 738,  and 
soon  after  was  married  to  the  young  woman  who  had  assisted 
him  and  had  waited  for  him  so  loyally.  He  settled  in  Stock- 
holm and  began  the  practice  of  medicine.  In  the  period  of 
his  absence  he  had  accomplished  much :  visited  Holland, 
England,  and  France,  formed  the  acquaintance  of  many 
eminent  naturalists,  obtained  his  medical  degree,  published 
numerous  w^orks  on  botany,  and  extended  his  fame  over  all 
Europe.  In  Stockholm,  however,  he  w^as  for  a  time  neglected, 
and  he  would  have  left  his  native  country  in  disgust  had  it 
not  been  for  the  dissuasion  of  his  wife. 

Professor  in  Upsala. — In  i  741  he  was  elected  professor 
of  anatomy  in  the  University  of  Upsala,  but  by  a  happy  stroke 
was  able  to  exchange  that  position  for  the  professorship  of 
botany,  materia  medica,  and  natural  history  that  had  fallen 
to  his  former  rival,  Rosen.  Linnaeus  was  now  in  his  proper 
element;  he  had  opportunity  to  lecture  on  those  subjects  to 
which  he  had  been  devotedly  attached  all  his  life,  and  he 
entered  upon  the  work  with  enthusiasm. 

He  attracted  numerous  students  by  the  power  of  his  per- 
sonal qualities  and  the  excellence  of  his  lectures.  He  became 
the  most  popular  professor  in  the  University  of  Upsala,  and, 
owing  to  his  drawing  power,  the  attendance  at  the  university 
was  greatly  increased.  In  1749  he  had  140  students  devoted 
to  studies  in  natural  histor)\  The  number  of  students  at 
the  university  had  been  about  500;  "  whilst  he  occupied  the 
chair  of  botany  there  it  rose  to  1,500."  A  part  of  this  in- 
crease w^as  due  to  other  causes,  but  Linnaeus  was  the  greatest 
single  drawing  force  in  the  university.  He  was  an  eloquent 
as  well  as  an  enthusiastic  lecturer,  and  he  aroused  great  in- 
terest among  his  students,  and  he  gave  an  astonishing  impulse 
to  the  study  of  natural  history  in  general,  and  to  botany  in  par- 
ticular.    Thus  Linnaeus,  after  having  passed  through  great 


124  BIOLOGY   AND    ITS    MAKERS 

privations  in  his  earlier  years,  found  himself,  at  the  age  of 
thirty-four,  established  in  a  position  which  brought  him  rec- 
ognition, honor,  and  large  emolument. 

In  May,  1907,  the  University  of  Upsala  celebrated  the 
two  hundredth  anniversary  of  his  birth  with  appropriate  cer- 


FiG.  34. — LiNN^us    AT   Sixty,   1707-1778. 

emonies.  Delegations  of  scientific  men  from  all  over  the 
world  were  in  attendance  to  do  honor  to  the  memory  of  the 
great  founder  of  biological  nomenclature. 


LINN^US    AND    NATURAL    HISTORY  12$ 

Personal  Appearance. — The  portrait  of  liinnaeus  at  the 
age  of  sixty  is  shown  in  Fig.  34.  He  was  described  as  of 
"  medium  height,  with  large  limbs,  brown,  piercing  eyes,  and 
acute  vision."  His  hair  in  early  youth  was  nearly  white,  and 
changed  in  his  manhood  to  brown,  and  became  gray  with 
the  advance  of  age.  Although  quick-tempered,  he  was  natu- 
rally of  a  kindly  disposition,  and  secured  the  affection  of  his 
students,  with  whom  he  associated  and  Vv^orked  in  the  most 
informal  way.  His  love  of  approbation  was  very  marked, 
and  he  was  so  much  praised  that  his  desire  for  fame  became 
his  dominant  passion.  The  criticism  to  which  his  work  was 
subjected  from,  time  to  time  accordingly  threw  him  into 
fits  of  despondency  and  rage. 

His  Influence  upon  Natural  History. — However  much  we 
miay  admire  the  industry  and  force  of  Linnxus,  we  must 
admit  that  he  gave  to  natural  history  a  one-sided  develop- 
ment, in  which  the  more  essential  parts  of  the  science  received 
scant  recognition.  His  students,  like  their  master,  w^ere 
mainly  collectors  and  classifiers.  "In  their  zeal  for  naming 
and  classifying,  the  higher  goal  of  investigation,  knowl- 
edge of  the  nature  of  animals  and  plants,  was  lost  sight  of 
and  the  interest  in  anatomy,  physiology,  and  embryolog}^ 
lagged." 

R.  Hertwig  says  of  him:  "For  while  he  in  his  Sy sterna 
Naturce  treated  of  an  extraordinarily  larger  number  of  ani- 
mals than  any  earlier  naturalist,  he  brought  about  no  deep- 
ening of  our  knowledge.  The  manner  in  which  he  divided 
the  animal  kingdom,  in  comparison  with  the  Aristotelian 
system,  is  to  be  called  rather  a  retrogression  than  an  advance. 
Tinnaeus  divided  the  animal  kingdom  into  six  classes — Mam- 
malia, Aves,  Amphibia,  Pisces,  Insecta,  Vermes.  The  first 
four  classes  correspond  to  Aristotle's  four  groups  of  animals 
with  blood.  In  the  division  of  the  invertebrated  animals  into 
Insecta  and  Vermes  Linnaeus  stands  undoubtedly  behind 


126  BIOLOGY    AND    ITS    MAKERS 

Aristotle,  who  attempted,  and  in  part  indeed  successfully,  to 
set  up  a  larger  number  of  groups. 

"But  in  his  successors  even  more  than  in  Linnaeus  himself 
we  see  the  damage  wrought  by  the  purely  systematic  method 
of  consideration.  The  diagnoses  of  Linnaeus  were  for  the 
most  part  models,  which,  mutatis  ynutandis, cowliXh^  employed 
for  new  species  with  little  trouble.  There  was  needed  only 
some  exchanging  of  adjectives  to  express  the  differences. 
With  the  hundreds  of  thousands  of  different  species  of 
anim.als,  there  was  no  lack  of  material,  and  so  the  arena  was 
opened  for  that  spiritless  zoology  of  species-making,  which 
in  the  first  half  of  the  nineteenth  century  brought  zoology 
into  such  discredit.  Zoology  would  have  been  in  danger  of 
growing  into  a  Tower  of  Babel  of  species-description  if  a 
counterpoise  had  not  been  created  in  the  strengthening  of  the 
physiologico-anatomical  method  of  consideration." 

His  Especial  Service. —Nevertheless,  the  vrork  of  Lin- 
naeus made  a  lasting  impression  upon  natural  history,  and  we 
shall  do  well  to  get  clearly  in  mind  the  nature  of  his  particular 
service.  In  the  first  place,  he  brought  into  use  the  method 
of  naming  animals  and  plants  which  is  employed  to-day.  Li 
his  Sysiema  NaturcB  and  in  other  publications  he  employed 
a  means  of  naming  every  natural  production  in  two  words^ 
and  it  is  therefore  called  the  binomial  nomenclature.  An 
illustration  will  make  this  clearer.  Those  animals  which  had 
close  resemblance,  like  the  lion,  tiger,  leopard,  the  lynx,  and 
the  cat,  he  united  under  the  common  generic  name  of  Felis^ 
and  gave  to  each  a  particular  trivial  name,  or  specific  nam.e. 
Thus  the  name  of  the  lion  became  Felis  leo,  of  the  tiger  Felis 
tigris,  of  the  leopard  Felis  pardus,  of  the  cat  Felis  calus ;  and 
to  these  the  modern  zoologists  have  added,  making  the 
Canada  lynx  Felis  Canadensis^  the  domestic  cat  Fells  domes- 
iicata,  etc.  In  a  similar  way,  the  dog-like  animals  were 
united  into  a  genus  designated  Canis,  and  the  particular 


LINN^US    AND    NATURAL    HISTORY  127 

kinds  or  species  became  Canis  lupus,  the  wolf,  Canis  vulpes^ 
the  fox,  Canis  jamiliaris,  the  common  dog.  This  simple 
method  took  the  place  of  the  var}dng  names  applied  to  the 
same  animal  in  different  countries  and  local  names  in  the 
same  country.  It  recognized  at  once  their  generic  likeness 
and  their  specific  individuality. 

All  animals,  plants,  and  minerals  were  named  according 
to  this  method.  Thus  there  were  introduced  into  nomencla- 
ture two  groups,  the  genus  and  the  species.  The  name  of 
the  genus  was  a  noun,  and  that  of  the  species  an  adjective 
agreeing  with  it.  In  the  choice  of  these  names  Linnaeus.- 
sought  to  express  some  distinguishing  feature  that  would  be 
suggestive  of  the  particular  animal,  plant,  or  mineral.  The 
trivial,  or  specific,  names  were  first  employed  by  Linnaeus  in 
1749,  and  were  introduced  into  his  Species  Plantarum  in 
1753,  and  into  the  tenth  edition  of  his  Systema  Naturce  in 

1758. 

We  recognize  Tinna^us  as  the  founder  of  nomenclature  in 
natural  history,  and  by  the  common  consent  of  naturalists, 
the  date  1758  has  come  to  be  accepted  as  the  starting-point 
for  determining  the  generic  and  specific  names  of  animals.. 
The  much  vexed  question  of  priority  of  names  for  animals  is- 
settled  by  going  back  to  the  tenth  edition  of  his  Systema  Na- 
/«r^,v/hile  the  botanists  have  adopted  his  Species  Plantarum,. 
1753,  as  their  base-line  for  names.  As  to  his  larger  divisions, 
of  animals  and  plants,  he  recognized  classes  and  orders.  Then 
came  genera  and  species.  Linnaeus  did  not  use  the  term 
family  in  his  formulae;  this  convenient  designation  was  lirst 
used  and  introduced  in  1780  by  Batch. 

The  Systema  Naturce  is  not  a  treatise  on  the  organization 
of  animals  and  plants ;  it  is  rather  a  catalogue  of  the  produc- 
tions of  nature  methodically  arranged.  His  aim  in  fact  was. 
not  to  give  full  descriptions,  but  to  make  a  methodical, 
arrangement. 


128  BIOLOGY   AND    ITS    MAKERS 

To  do  justice,  however,  to  the  discernment  of  Linnaeus,  it 
should  be  added  that  he  was  fully  aware  of  the  artificial 
nature  of  his  classification.  As  Kerner  has  said:  ''It  is  not 
the  fault  of  this  accomplished  and  renowned  naturalist  if  a 
greater  importance  were  attached  to  his  system  than  he  him- 
self ever  intended.  Linnaeus  never  regarded  his  twenty-four 
classes  as  real  and  natural  divisions  of  the  vegetable  kingdom, 
and  specifically  says  so ;  it  was  constructed  for  convenience  of 
reference  and  identification  of  species.  A  real  natural  system, 
founded  on  the  true  affinities  of  plants  as  indicated  by  the 
structural  characters,  he  regarded  as  the  highest  aim  of  botan- 
ical endeavor.  He  never  completed  a  natural  system,  leaving 
only  a  fragment  (published  in  1738)." 

Terseness  of  Descriptions. — His  descriptions  were  marked 
by  extreme  brevity,  but  by  great  clearness.  This  is  a  second 
feature  of  his  work.  In  giving  the  diagnosis  of  a  form  he 
was  very  terse.  He  did  not  employ  fully  formed  sentences 
containing  a  verb,  but  words  concisely  put  together  so  as  to 
bring  out  the  chief  things  he  wished  to  emphasize.  As  an 
illustration  of  this,  we  may  take  his  characterization  of  the 
forest  rose,  ^^  Rosa  sylvestris  vulgaris,  jlore  odorata  incarnato.''^ 
The  common  rose  of  the  forest  with  a  flesh-colored,  sweet- 
smelling  flower.  In  thus  fixing  the  attention  upon  essential 
points  he  got  rid  of  verbiage,  a  step  that  was  of  very  great 
importance. 

His  Idea  of  Species. — A  third  feature  of  his  work  was 
that  of  emphasizing  the  idea  of  species.  In  this  he  built 
upon  the  work  of  Ray.  We  have  already  seen  that  Ray 
was  the  first  to  define  species  and  to  bring  the  conception 
into  natural  history.  Ray  had  spoken  of  the  variability  of 
species,  but  Linnaeus,  in  his  earUer  publications,  declared 
that  they  were  constant  and  invariable.  His  conception  of  a 
species  was  that  of  individuals  born  from  similar  parents. 
It  was  assumed  that  at  the  original  stocking  of  the  earth,  one 


LINN^US    AND    NATURAL    HISTORY  129 

pair  of  each  kind  of  animals  was  created,  and  that  existing 
species  were  the  direct  descendants  without  change  of  form 
or  habit  from  the  original  pair.  As  to  their  number,  he  said : 
^^ Species  tot  sunt,  quot  jormce  ah  initio  created  sunt^^ — there 
are  just  so  many  species  as  there  were  forms  created  in  the 
beginning;  and  his  oft-quoted  remark,  "iVw//a  species  nova,^^ 
indicates  in  terse  language  his  position  as  to  the  formation  of 
new  species.  Linnaeus  took  up  this  idea  as  expressing  the  cur- 
rent thought,  without  analysis  of  what  was  involved  in  it.  He 
readily  might  have  seen  that  if  there  were  but  a  single  pair 
of  each  kind,  some  of  them  must  have  been  sacrificed  to 
tlie  hunger  of  the  carnivorous  kinds ;  but,  better  than  making 
any  theories,  he  might  have  looked  for  evidence  in  nature  as 
to  the  fixity  of  species. 

While  Linnaeus  first  pronounced  upon  the  fixity  of  species, 
it  is  interesting  to  note  that  his  extended  observations  upon 
nature  led  him  to  see  that  variation  among  animals  and  plants 
is  common  and  extensive,  and  accordingly  in  the  later  editions 
of  his  Systema  Nattirce  we  find  him  receding  from  the  position 
that  species  are  fixed  and  constant.  Nevertheless,  it  was 
owing  to  his  influence,  more  than  to  that  of  any  other  writer 
of  the  period,  that  the  dogma  of  fixity  of  species  was  estab- 
lished. His  great  contemporary  Buffon  looked  upon  species 
as  not  having  a  fixed  reality  in  nature,  but  as  being  fig- 
ments of  the  imagination ;  and  we  shall  see  in  a  later  section 
of  this  book  how  the  idea  of  Linnaeus  in  reference  to  the 
fixity  of  species  gave  way  to  accumulating  evidence  on  the 
matter. 

Summary. — The  chief  services  of  Linnaeus  to  natural 
science  consisted  of  these  three  things :  bringing  into  current 
use  the  binomial  nomenclature,  the  introduction  of  terse 
formulae  for  description,  and  fixing  attention  upon  species. 
The  first  two  were  necessary  steps ;  they  introduced  clearness 
and  order  into  the  management  of  the  immense  number  of 


130  BIOLOGY   AND    ITS    MAKERS 

details,  and  they  made  it  possible  for  the  observations  and 
discoveries  of  others  to  be  understood  and  to  take  their  place 
in  the  great  system  of  which  he  was  the  originator.  The 
effect  of  the  last  step  was  to  direct  the  attention  of  naturalists 
to  species,  and  thereby  to  pave  the  way  for  the  coming  con- 
sideration of  their  origin,  a  consideration  which  became  such 
a  burning  Ci[uestion  in  the  last  half  of  the  nineteenth  century. 


Reform  of  the  Linn^an  System 

Necessity  of  Reform. — ^As  indicated  above,  the  classifica- 
tion established  by  Linnaeus  had  grave  defects;  it  was  not 
founded  on  a  knowledge  of  the  comparative  structure  of 
animals  and  plants,  but  in  many  instances  upon  superficial 
features  that  were  not  distinctive  in  determining  their  position 
and  relationships.  His  system  was  essentially  an  artificial 
one,  a  convenient  key  for  finding  the  names  of  animals  and 
plants,  but  doing  violence  to  the  natural  arrangement  of  those 
organisms.  An  illustration  of  this  is  seen  in  his  classification 
of  plants  into  classes,  mainly  on  the  basis  of  the  number  of 
stamens  in  the  flower,  and  into  orders  according  to  the  number 
of  pistils.  Moreover,  the  true  object  of  investigation  was 
obscured  by  the  Linnaean  system.  The  chief  aim  of  bio- 
logical study  being  to  extend  our  knowledge  of  the  structure, 
development,  and  physiology  of  animals  and  plants  as  a 
means  of  understanding  more  about  their  life,  the  arrange- 
ment of  animals  and  plants  into  groups  should  be  the  out- 
come of  such  studies  rather  than  an  end  in  itself. 

It  was  necessary  to  follow  different  methods  to  bring 
natural  histor}^  back  into  the  line  of  true  progress.  The  first 
modification  of  importance  to  the  Linnaean  system  was  that 
of  Cuvier,  who  proposed  a  grouping  of  animals  based  upon 
a  knowledge  of  their  comparative  anatomy.     He  declared 


LINN^US    AND    NATURAL    HISTORY  131 

that  animals  exhibit  four  types  of  organization,  and  his  types 
were  substituted  for  the  primary  groups  of  Linnaeus. 

The  Scale  of  Being. — In  order  to  understand  the  bearing 
of  Cuvier's  conclusions  we  must  take  note  of  certain  views 
regarding  the  animal  kingdom  that  were  generally  accepted 
at  the  time  of  his  w-riting.  Between  Linnceus  and  Cuvier 
there  had  emerged  the  idea  that  all  animals,  from  the  lowest 
to  the  highest,  form  a  graduated  series.  This  grouping  of 
animals  into  a  linear  arrangement  was  called  exposing  the 
Scale  of  Being,  or  the  Scale  of  Nature  (Scala  Naturce). 
Buffon,  Lamarck,  and  Bonnet  were  among  the  chief  ex- 
ponents of  this  idea. 

That  Lamarck's  connection  with  it  was  temporary  has 
been  generally  overlooked.  It  is  the  usual  statement  in  the 
histories  of  natural  science,  as  in  the  Encyclopcedia  Britannica, 
in  the  History  of  Carus,  and  in  Thomson's  Science  oj  Lije, 
that  the  idea  of  the  scale  of  nature  found  its  fullest  expression 
in  Lamarck.  Thomson  says :  "  His  classification  (1801-1812) 
represents  the  climax  of  the  attempt  to  arrange  the  groups 
of  animals  in  linear  order  from  lower  to  higher,  in  what  was 
called  a  scala  naturce^^  (p.  14).  Even  so  careful  a  writer  as 
Richard  Hertwig  has  expressed  the  matter  in  a  similar  form. 
Now,  while  Lamarck  at  first  adopted  a  linear  classification, 
it  is  only  a  partial  reading  of  his  works  that  will  support  the 
conclusion  that  he  held  to  it.  In  his  Systeme  des  Animaux 
sans  Vertebres,  published  in  1801,  he  arranged  animals  in 
this  way;  but  to  do  credit  to  his  discernment,  it  should  be 
observed  that  he  was  the  first  to  employ  a  genealogical  tree 
and  to  break  up  the  serial  arrangement  of  animal  forms.  In 
1809,  in  the  second  volume  of  his  Philosophie  Zoologique, 
as  Packard  has  pointed  out,  he  arranged  animals  according 
to  their  relationships,  in  the  form  of  a  trunk  with  divergent 
branches.  This  was  no  vague  suggestion  on  his  part,  but 
an  actual  pictorial  representation  of  the  relationship  between 


132  BIOLOGY   AND    ITS    MAKERS 

different  groups  of  animals,  as  conceived  by  him.  Although 
a  crude  attempt,  it  is  interesting  as  being  the  first  of  its  kind. 
This  is  so  directly  opposed  to  the  idea  of  scale  of  being  that 
we  make  note  of  the  fact  that  Lamarck  forsook  that  view  at 
least  twenty  years  before  the  close  of  his  life  and  substituted 
for  it  that  of  the  genealogical  tree. 

Lamarck's  Position  in  Science. — Lamarck  is  coming  into 
full  recognition  for  his  part  in  founding  the  evolution  theor}', 
but  he  is  not  generally,  as  yet,  given  due  credit  for  his  work 
in  zoology.  He  was  the  most  philosophical  thinker  engaged 
with  zoology  at  the  close  of  the  eighteenth  and  the  beginning 
of  the  nineteenth  century.  He  was  greater  than  Cuvier  in 
his  reach  of  intellect  and  in  his  discernment  of  the  true 
relationships  among  living  organisms.  We  are  to  recollect 
that  he  forsook  the  dogma  of  fixity  of  species,  to  which  Cuvier 
held,  and  founded  the  first  comprehensive  theory  of  organic 
evolution.  To-day  we  can  recognize  the  superiority  of  his 
mental  grasp  over  that  of  Cuvier,  but,  owing  to  the  personal 
magnetism  of  the  latter  and  to  his  position,  the  ideas  of 
Lamarck,  which  Cuvier  com.bated,  received  but  little  atten- 
tion when  they  were  promulgated.  We  shall  have  occasion 
in  a  later  chapter  to  speak  more  fully  of  Lamxarck's  contribu- 
tion to  the  progress  of  biological  thought. 

Cuvier's  Four  Branches. — We  now  return  to  the  type- 
theory  of  Cuvier.  By  extended  studies  in  comparative  anat- 
omy, he  came  to  the  conclusion  that  animals  are  constructed 
upon  four  distinct  plans  or  types:  the  vertebrate  type;  the 
moUuscan  type;  the  articulated  type,  embracing  animals  with 
joints  or  segments;  and  the  radiated  type,  the  latter  with  a 
radial  arrangement  of  parts,  like  the  starfish;  etc.  These 
types  are  distinct,  but  their  representatives,  instead  of  forming 
a  linear  series,  overlap  so  that  the  lowest  forms  of  one  of  the 
higher  groups  are  simpler  in  organization  than  the  higher 
forms  of  a  lower  group.     This  was  very  illuminating,  and, 


LINN^US    AND    NATURAL   HISTORY  133 

being  founded  upon  an  analysis  of  structure,  was  important. 
It  was  directly  at  variance  with  the  idea  of  scale  of  being,  and 
overthrew  that  doctrine. 

Cuvier  first  expressed  these  views  in  a  pamphlet  ])ublished 
in  1795,  and  later  in  a  better-known  paper  read  before  the 
French  Academy  in  181 2,  but  for  the  full  development  of 
his  type-theor}^  we  look  to  his  great  volume  on  the  animal 
kingdom  published  in  1816.  The  central  idea  of  his  arrange- 
ment is  contained  in  the  secondary  title  of  his  book,  "The 
Animal  Kingdom  Arranged  According  to  its  Organization  '^ 
{Le  Re gne  Animal  Distrihued'aprhs  son  Organisation,  1816). 
The  expression  "arranged  according  to  its  organization" 
embraces  the  feature  in  which  this  analysis  of  animals  differs 
from  all  previous  attempts. 

Correlation  of  Parts. — ^An  important  idea,  first  clearly 
expressed  by  Cuvier,  was  that  of  correlation  of  parts.  The 
view  that  the  different  parts  of  an  animal  are  so  correlated 
that  a  change  in  one,  brought  about  through  changes  in  use, 
involves  a  change  in  another.  For  illustration,  the  cleft  hoof 
is  always  associated  with  certain  forms  of  teeth  and  with  the 
stomach  of  a  ruminant.  The  sharp  claws  of  flesh-eating 
animals  are  associated  with  sharp,  cutting  teeth  for  tearing 
the  flesh  of  the  victims,  and  with  an  alimentary  tube  adapted 
to  the  digestion  of -a  fleshy  diet.  Further  account  of  Cuvier 
is  reserved  for  the  chapter  on  the  Rise  of  Comparative  Anat- 
omy, of  which  he  was  the  founder. 

Von  Baer. — The  next  notable  advance  affecting  natural 
history  came  through  the  work  of  Von  Baer,  who,  in  1828, 
founded  the  science  of  development  of  animal  forms.  He 
arrived  at  substantially  the  same  conclusions  as  Cuvier. 
Thus  the  system  founded  upon  -  comparative  anatomy  by 
Cuvier  came  to  have  the  support  of  Von  Baer's  studies  in 
embr}^ology. 

The  contributions  of  these  men  proved  to  be  a  turning- 


134  BIOLOGY   AND    ITS    MAKERS 

point  in  natural  history,  and  subsequent  progress  in  system- 
atic botany  and  zoology  resulted  from  the  application  of  the 
methods  of  Cuvier  and  Von  Baer,  rather  than  from  following 
that  of  Linnaeus.  His  nomenclature  remained  a  permanent 
contribution  of  value,  but  the  knowledge  of  the  nature  of 
living  forms  has  been  advanced  chiefly  by  studies  in  com- 
parative anatomy  and  embryology,  and,  also,  in  the  applica- 
tion of  experiments. 

The  most  significant  advances  in  reference  to  the  class- 
ification of  animals  was  to  come  as  a  result  of  the  accept- 
ance of  the  doctrine  of  organic  evolution,  subsequent  to 
1859.  Then  the  relationships  between  animals  were  made 
to  depend  upon  community  of  descent,  and  a  distinction 
was  drawn  between  superficial  or  apparent  relationships 
and  those  deep-seated  characteristics  that  depend  upon  close 
genetic  aihnities. 

Alterations  by  Von  Siebold  and  Leuckart. — But,  in  the 
mean  time,  naturalists  were  not  long  in  discovering  that  the 
primary  divisions  established  by  Cuvier  were  not  well  bal- 
anced, and,  indeed,  that  they  were  not  natural  divisions  of 
the  animal  kingdom.  The  group  Radiata  was  the  least 
sharply  defined,  since  Cuvier  had  included  in  it  not  only  those 
animals  which  exhibit  a  radial  arrangement  of  parts,  but  also 
unicellular  organisms  that  were  asymmetrical,  and  some  of 
the  worms  that  showed  bilateral  symmetry.  Accordingly, 
Karl  Th.  von  Siebold,  in  1845,  separated  these  animals  and 
redistributed  them.  For  the  simplest  unicellular  animals  he 
adopted  the  name  Protozoa,  which  they  still  retain,  and  the 
truly  radiated  forms,  as  starfish,  sea-urchins,  hydroid  polyps, 
coral  animals,  etc.,  were  united  in  the  group  Zoophyta.  Von 
Siebold  also  changed  Cuvier's  branch,  Articulata,  separating 
those  forms  as  Crustacea,  insects,  spiders,  and  myriopods, 
which  have  jointed  appendages,  into  a  natural  group  called 
Arthropoda,  and  uniting  the  segmented  worms  with  those 


LINN^US    AND    NATURAL    HISTORY 


135 


worms  that  Cuvier  has  included  in  the  radiate  group,  into 
another  branch  called  Vermes.  This  separation  of  the  four 
original  branches  of  Cuvier  was  a  movement  in  the  right 
direction,  and  v/as  destined  to  be  carried  still  farther. 


Fig.  35. — Karl  Th.  von  Siebold,  1804-1885. 


Von  Siebold  (Fig.  35)  was  an  important  man  in  the 
progress  of  zoology,  especially  in  reference  to  the  comparative 
anatomy  of  the  invertebrates. 

Leuckart  (Fig.  36),  whose  fame  as  a  lecturer  and  teacher 


136 


BIOLOGY   AND    ITS    MAKERS 


attracted  many  young  men  to  the  University  of  Leipsic,  is 
another  conspicuous  personality  in  zoological  progress. 

This  distinguished  zoologist,  following  the  lead  of  Von 
Siebold,  made  further  modifications.  He  split  Von  Siebold's 
group  of  Zoophytes  into  two  distinct  kinds  of  radiated  animals: 


Fig.  36. — Rudolph  Leuckart,   1823-1898. 


the  star-fishes,  sea-urchins,  sea-cucumbers,  etc.,  Imving  a 
spiny  skin,  he  designated  Echinoderma;  the  jelly-fishes,, 
polyps,  coral  animals,  etc.,  not  possessing  a  true  body  cavity ^ 
were  also  united  into  a  natural  group,  for  v/hich  he  proposed 
the  name  Coelenterata. 

From  all  these  changes  there  resulted  the  seven  primary 


LINN^US    AND    NATURAL    HISTORY  137 

divisions— branches,  subkingdoms,  or  phyla — ^v^^hich,  with 
small  modifications,  are  still  in  use.  These  are  Protozoa, 
Coelenterata,  Echinoderma,  Vermes,  Arthropoda,  Mollusca, 
Vertebrata.  These  seven  phyla  are  not  entirely  satisfactory, 
and  there  is  being  carried  on  a  redistribution  of  forms,  as  in 
the  case  of  the  brachiopods,  the  sponges,  the  tunicates,  etc. 
While  all  this  makes  toward  progress,  the  changes  are  of 
more  narrow  compass  than  those  alterations  due  to  Von 
Siebold  and  Leuckart. 

Summary. — In  reviewing  the  rise  of  scientific  natural 
history,  we  observe  a  steady  development  from  the  time  of 
the  Physiologus,  first  through  a  return  to  Aristotle,  and 
through  gradual  additions  to  his  observations,  notably  by 
Gesner,  and  then  the  striking  improvements  due  to  Ray  and 
Linnaeus.  We  may  speak  of  the  latter  two  as  the  founders 
of  systematic  botany  and  zoology.  But  the  system  left  by 
Linnaeus  was  artificial,  and  the  greatest  obvious  need  was  to 
convert  it  into  a  natural  system  founded  upon  a  knowledge 
of  the  structure  and  the  development  of  living  organisms. 
This  was  begun  by  Cuvier  and  Von  Baer,  and  was  continued 
especially  by  Von  Siebold  and  Leuckart.  To  this  has  been 
added  the  study  of  habits,  breeding,  and  adaptations  of  or- 
ganisms, a  study  which  has  given  to  natural  history  much 
greater  importance  than  if  it  stood  merely  for  the  systematic 
classification  of  animals  and  plants. 

Tabular  View  of  Classifications. — ^A  table  showing  the 
primar}^  groups  of  Linnaeus,  Cuvier,  Von  Siebold,  and 
Leuckart  will  be  helpful  in  picturing  to  the  mind  the  modifi- 
cations made  in  the  classification  of  animals.  Such  a  table 
is  given  on  the  following  page. 

L.  Agassiz,  in  his  famous  essay  on  Classification,  reviews 
in  the  most  scholarly  way  the  various  systems  of  classifica- 
tion. One  peculiar  feature  of  Agassiz's  philosophy  was  his 
adherence  to  the  dogma  of  the  fixity  of  species.     The  same 


133 


BIOLOGY   AND    ITS    MAKERS 


year  that  his  essay  referred  to  was  published  (1859)  appeared 
Darwin's  Origin  of  Species.  Agassiz,  however,  was  never 
able  to  accept  the  idea  of  the  transformations  of  species. 


Linnaeus 

Cuvier 

Von  Siebold 

Leuckart 

Mammalia 

Vertebrata 

Vertebrata 

Vertebrata 

Aves 

(Embracing  five 
classes:  Mam- 

(Embracing five 
classes.) 

(Five  classes.) 

Amphibia 

malia,  Aves,    Rep- 
tilia,  Batrachia, 

Pisces 

Pisces.) 

Insecta 

MoUusca 

Mollusca 

Mollusca 

(Including  Crusta- 
cea, etc.) 

Articulata 

(  Arthropoda 
(  Vermes 

Arthropoda 

Vermes 

(Including    Mol- 
lusca  and  all 
lower  forms.) 

Radiata 

r  Zoophyta 

(  Protozoa 

Vermes 
\  Echinoderma 
}  Coelenterata 

Protozoa 

Steps  in  Biological  Progress  from  Linn^us  to  Darwin 


The  period  from  Linnaeus  to  Darwin  is  one  full  of  im- 
portant advances  for  biology  in  general.  We  have  considered 
in  this  chapter  only  those  features  that  related  to  changes  in 
the  system  of  classification,  but  in  the  mean  time  the  morpho- 
logical and  the  physiological  sides  of  biology  were  being  ad- 
vanced not  only  by  an  accumulation  of  facts,  but  by  their 
better  analysis.  It  is  an  interesting  fact  that,  although  during 
this  period  the  details  of  the  subject  were  greatly  multiplied, 
progress  was  relatively  straightforward  and  by  a  series  of 
steps  that  can  be  clearly  indicated. 

It  will  be  of  advantage  before  the  subject  is  taken  up  in 
its  parts  to  give  a  brief  forecast  in  which  the  steps  of  prog- 
ress can  be  represented  in  outline  without  the  confusion 
arising  from  the  consideration  of  details.  Geddes,  in  1898, 
pointed  out  the  steps  in  progress,  and  the  account  that  follows 
is  based  upon  his  lucid  analysis. 


LINN^US    AND    NATURAL    HISTORY  139 

The  Organism. — In  the  time  of  Linnaeus  the  attention  of 
naturalists  was  mainly  given  to  the  organism  as  a  whole. 
Plants  and  animals  were  considered  from  the  standpoint  of 
the  organism — the  external  features  w^ere  largely  dealt  with, 
the  habitat,  the  color,  and  the  general  appearance — features 
which  characterize  the  organism  as  a  whole.  Linnaeus  and 
Jussieu  represent  this  phase  of  the  work,  and  Buffon  the 
higher  type  of  it.  Modern  studies  in  this  line  are  like  addi- 
tion to  the  Systema  Naturce. 

Organs. — The  first  distinct  advance  came  in  investigating 
animals  and  plants  according  to  their  structure.  Instead 
of  the  complete  organism,  the  organs  of  which  it  is  composed 
became  the  chief  subject  of  analysis.  The  organism  was 
dissected,  the  organs  were  examined  broadly,  and  those  of 
one  kind  of  animal  and  plant  compared  with  another.  This 
kind  of  comparative  study  centered  in  Cuvier,  w^ho,  in  the 
early  part  of  the  nineteenth  century,  founded  the  science  of 
comparative  anatomy  of  animals,  and  in  Hofmeister,  who 
examined  the  structure  of  plants  on  a  basis  of  broad  com- 
parison. 

Tissues. — Bichat,  the  famous  contemporary  of  Cuvier, 
essayed  a  deeper  level  of  analysis  in  directing  attention  to  the 
tissues  that  are  combined  to  make  up  the  organs.  He  dis- 
tinguished tw^enty-one  kinds  of  tissues  by  combinations  of 
which  the  organs  are  comxposed.  This  step  laid  the  founda- 
tion for  the  science  of  histology,  or  minute  anatomy.  Bichat 
called  it  general  anatomy  {Anatomie  Generate,  1801). 

Cells. — Before  long  it  was  shown  that  tissues  are  not  the 
real  units  of  structure,  but  that  they  are  composed  of  micro- 
scopic elements  called  cells.  This  level  of  analysis  was  not 
reached  until  magnifying-lenses  wxre  greatly  improved — 
it  was  a  product  of  a  closer  scrutiny  of  nature  with  improved 
instruments.  The  foundation  of  the  work,  especially  for 
plants,  had  been  laid  by  Leeuwenhoek,  Malpighi,  and  Grew^ 


I40  BIOLOGY   AND    ITS   MAKERS 

But  when  the  broad  generah'zation,  that  all  the  tissues  of 
animals  and  plants  are  composed  of  cells,  was  given  to  the 
world  by  Schleiden  and  Schwann,  in  1838-39,  the  entire  or- 
ganization of  living  forms  took  on  a  new  aspect.  This  was 
progress  in  understanding  the  morphology  of  animals  and 
plants. 

Protoplasm. — With  improved  microscopes  and  attention 
directed  to  cells,  it  was  not  long  before  the  discovery  was 
made  that  the  cells  as  units  of  structure  contain  protoplasm. 
That  this  substance  is  similar  in  plants  and  animals  and  is 
the  seat  of  all  vital  activity  was  determined  chiefly  by  the 
researches  of  Max  Schultze,  published  in  1861.  Thus  step 
by  step,  from  1758,  the  date  of  the  tenth  edition  of  the 
System  a  Natures,  to  1861,  there  was  a  progress  on  the  mor- 
phological side,  passing  from  the  organism  as  a  whole  to 
organs,  to  tissues,  to  cells,  and  finally  to  protoplasm,  the  study 
of  which  in  all  its  phases  is  the  chief  pursuit  of  biologists. 

The  physiological  side  had  a  parallel  development.  In 
the  period  of  Linnaeus,  the  physiology  of  the  organism  was 
investigated  by  Haller  and  his  school;  following  him  the 
physiology  of  organs  and  tissues  was  advanced  by  J.  Miiller, 
Bichat,  and  others.  Later,  Virchow  investigated  the  physiol- 
ogy of  cells,  and  Claude  Bernard  the  chemical  activities  of 
protoplasm. 

This  set  forth  in  outline  will  be  amplified  in  the  follow- 
ing chapters. 


CHAPTER    VII 

CUVIER  AND  THE  RISE  OF  COMPARATIVE 
ANATOMY 

After  observers  like  Linnaeus  and  his  followers  had  at- 
tained a  knowledge  of  the  externals,  it  was  natural  that  men 
should  turn  their  attention  to  the  organization  or  internal 
structure  of  living  beings,  and  when  the  latter  kind  of  inves- 
tigation became  broadly  comparative,  it  blossomed  into  com- 
parative anatomy.  The  materials  out  of  which  the  science 
of  comparative  anatomy  was  constructed  had  been  long 
accumulating  before  the  advent  of  Cuvier,  but  the  mass  of 
details  had  not  been  organized  into  a  compact  science. 

As  indicated  in  previous  chapters,  there  had  been  an  in- 
creasing number  of  studies  upon  the  structure  of  organisms, 
both  plant  and  animal,  and  there  had  resulted  some  note- 
worthy monographs.  All  this  work,  however,  was  mainly 
descriptive,  and  not  comparative.  Now  and  then,  the  com- 
paring tendency  had  been  shown  in  isolated  writings  such  as 
those  of  Harvey,  Malpighi,  and  others.  As  early  as  1555, 
Belon  had  compared  the  skeleton  of  the  bird  with  that  of  the 
human  body  "in  the  same  posture  and  as  nearly  as  possible 
bone  for  bone  " ;  but  this  was  merely  a  faint  foreshadowing 
of  what  was  to  be  done  later  in  comparing  the  systems  of  the 
more  important  organs. 

We  must  keep  in  mind  that  the  study  of  anatomy  em- 
braces not  merely  the  bony  framework  of  animals,  but  also 
the  muscles,  the  nervous  system,  the  sense  organs,  and  all  the 
other  structures  of  both  animals  and  plants.     In  the  rise  of 

141 


142 


BIOLOGY   AND    ITS    MAKERS 


comparative  anatomy  there  gradually  emerged  naturalists 
who  compared  the  structure  of  the  higher  animals  with  that 
of  the  simpler  ones.  These  comparisons  brought  out  so 
many  resemblances  and  so  many  remarkable  facts  that  anat- 


FiG.  37. — Severinus,   1580-1656. 


omy,  which  seems  at  first  a  dry  subject,  became  endued  with 
great  interest. 

Severinus. — The  first  book  expressly  devoted  to  compara- 
tive anatomy  was  that  of  Severinus  (i  580-1656),  designated 


RISE    OF    COMPARATIVE    ANATOMY  143 

Zootomia  DemocritcB.  The  title  was  derived  from  the  Roman 
naturalist  Democritaeus,  and  the  date  of  its  publication,  1645, 
places  the  treatise  earlier  than  the  works  of  Malpighi,  Leeu- 
wenhoek,  and  Swammerdam.  The  book  is  illustrated  by 
numerous  coarse  woodcuts,  showing  the  internal  organs  of 
fishes,  birds,  and  some  mammals.  There  are  also  a  few- 
illustrations  of  stages  in  the  development  of  these  animals. 
The  comparisons  were  superficial  and  incidental ;  neverthe- 
less, as  the  first  attempt,  after  the  revival  of  anatomy,  to 
make  the  subject  comparative,  it  has  some  especial  interest. 
Severinus  (Fig.  37)  should  be  recognized  as  beginning  the 
line  of  comparative  anatomists  which  led  up  to  Cuvier. 

Forerunners  of  Cuvier. — ^Anatomical  studies  began  to 
take  on  broad  features  with  the  work  of  Camper,  John 
Hunter,  and  Vicq  d'Azyr.  These  three  men  paved  the  way 
for  Cuvier,  but  it  must  be  said  of  the  two  former  that  their 
comparisons  were  limited  and  unsystematic. 

Camper,  whose  portrait  is  shown  in  Fig.  38,  was  born  in 
Leyden,  in  1722.  He  was  a  versatile  man,  having  a  taste 
for  drawing,  painting,  and  sculpture,  as  well  as  for  scientific 
studies.  He  received  his  scientific  training  under  Boerhaavc 
and  other  eminent  men  in  Leyden,  and  became  a  professor 
and,  later,  rector  in  the  University  of  Groningen.  Possessing 
an  ample  fortune,  and  also  having  married  a  rich  wife,  he 
was  in  position  to  foilov/  his  ov/n  tastes.  He  travelled  exten- 
sively and  gathered  a  large  collection  of  skeletons.  He 
showed  considerable  talent  as  an  anatomist,  and  he  made 
several  discoveries,  which,  however,  he  did  not  develop,  but 
left  to  others.  Perhaps  the  possession  of  riches  was  one  of 
his  limitations;    at  any  rate,  he  lacked  fixity  of  purpose. 

Among  his  discoveries  may  be  mentioned  the  semicircu- 
lar canals  in  the  ear  of  fishes,  the  fact  that  the  bones  of  flying 
birds  are  permeated  by  air,  the  determination  of  some  fossil 
bones,  with  the  suggestion  that  they  belonged  to  extinct  forms. 


144 


BIOLOGY   AND    ITS    MAKERS 


The  latter  point  is  of  interest,  as  antedating  the  conchisions 
of  Cuvier  regarding  the  nature  of  fossil  bones.  Camper  also 
made  observations  upon  the  facial  angle  as  an  index  of  in- 
telligence in  the  different  races  of  mankind,  and  in  lower 


'-fefei 

-<^'^""--. 

if    ■ 

# 

mki/snf 

HHL  '*  ^«^Ni|M|  ^lO^^^^^I 

^s 

i^K_               '■'•-'  ^^^k?w.   ''^'.^II^^^H^II^I 

1 

% 

MM 

fe' 

1 

1      jj 

'^.' 

Fig.  38. — Camper,   i 722-1 789. 


animals.     He  studied  the  anatomy  of  the  elephant,  the  whale, 
the  orang,  etc. 

John  Hunter  (1728-1793),  the  gifted  Scotchman  whose 
museum  in  London  has  been  so  justly  celebrated,  was  a  man 
of  extraordinary  originality,  who  read  few  books  but  went 
directly  to  nature  for  his  facts ;  and,  although  he  made  errors 
from  which  he  would  have  been  saved  by  a  wider  acquaint- 


RISE    OF    COMPARATIVE    ANATOMY 


145 


ance  with  the  writings  of  naturalists,  his  neglect  of  reading 
left  his  mind  unprejudiced  by  ihe  views  of  others.  He  was 
a  wild,  unruly  spirit,  who  would  not  be  forced  into  the  con- 
ventional mold  as  regards  either  education  or  manners. 
His  okicr  brother,  William,  a  man  of  more  elegance  and 
refinement,  who  well  understood  the  value  of  polish  in  refer- 


FiG.  39. — John  Hunter,   i 728-1 793. 


ence  to  worldly  success,  tried  to  improve  John  by  arranging 
for  him  to  go  to  the  University  of  Oxford,  but  John  rebelled 
and  would  not  have  the  classical  education  of  the  university, 
nor  would  he  take  on  the  refinements  of  taste  and  manner  of 
which  his  brother  was  a  good  example.  *'  Why,"  the  doughty 
John  is  reported  to  have  said,  "  they  wanted  to  make  me  study 


146  BIOLOGY   AND    ITS    MAKERS 

Greek!  They  tried  to  make  an  old  woman  of  me!"  How- 
ever much  lack  of  appreciation  this  attitude  indicated,  it 
shows  also  the  Philistine  independence  of  his  spirit.  This 
independence  of  mind  is  one  of  his  striking  characteristics. 

This  is  not  the  place  to  dwell  upon  tlie  unfortunate  con- 
troversy that  arose  betv/een  these  two  illustrious  brothers 
regarding  scientific  discoveries  claimed  by  each.  The  posi- 
tion of  both  is  secure  in  the  historical  development  of  medicine 
and  surgery.  Although  the  work  of  John  Hunter  Avas  largely 
medical  and  surgical,  he  also  made  extensive  studies  on  the 
comparative  anatomy  of  animals,  and  has  a  place  as  one  of 
the  most  conspicuous  predecessors  of  Cuvier.  He  was  very 
energetic  both  in  making  discoveries  and  in  adding  to  his 
great  museum. 

The  original  collections  made  by  Hunter  are  still  open  to 
inspection  in  the  rooms  of  the  Royal  College  of  Surgeons, 
London.  It  was  his  object  to  preserve  specimens  to  illus- 
trate the  phenomena  of  life  in  all  organisms,  whether  in 
health  or  disease,  and  the  extent  of  his  museum  may  be 
divined  from  the  circumstance  that  he  expended  upon  it 
about  three  hundred  and  seventy-five  thousand  dollars.  Al- 
though he  described  and  compared  many  types  of  animals, 
it  was  as  maich  in  bringing  this  collection  together  and  leaving 
it  to  posterity  that  he  advanced  comparative  anatomy  as  in 
what  he  wrote.  After  his  death  the  House  of  Commons 
purchased  his  museum  for  fifteen  thousand  pounds,  and 
placed  it  under  the  care  of  the  corporation  of  Surgeons. 
Hunter's  portrait  is  shown  in  Fig.  39. 

Vicq  d'Azyr  (P'ig.  40),  more  than  any  other  man,  holds 
the  chief  rank  as  a  comparative  anatomist  before  the  advent 
of  Cuvier  into  the  same  field.  He  was  born  in  1748,  the  son 
of  a  physician,  and  went  to  Paris  at  the  age  of  seventeen  to 
study  medicine,  remaining  in  the  metropolis  to  the  time  of 
his  death  in  1 794.     He  was  celebrated  as  a  physician,  became 


RISE   OF   COMPARATIVE   ANATOMY  147 

permanent  secretary  of  the  newly  founded  Academy  of  Med- 
icine, consulting  physician  to  the  queen,  and  occupied  other 
positions  of  trust  and  responsibility.  He  married  the  niece 
of  Daubenton,  and,  largely  through  his  influence,  was  ad- 
vanced to  social  place  and  recognition.  On  the  death  of 
Buffon,  in  1788,  he  took  the  seat  of  that  distinguished  nat- 
uralist as  a  member  of  the  French  Academ^y. 


Fig.  40. — VicQ  d'Azyr,   i  748-1 794. 

He  made  extensive  studies  upon  the  organization  particu- 
larly of  birds  and  quadrupeds,  making  comparisons  between 
their  structure,  and  bringing  out  new  points  that  were  supe- 
rior to  anything  yet  published.  His  comparisons  of  the  limbs 
of  man  and  animals,  showing  a  correspondence  between  the 
flexor  and  extensor  muscles  of  the  legs  and  arms,  were  made 
with  great  exactness,  and  they  served  to  mark  the  beginning 
of  a  new  kind  of  precise  comparison.  These  were  not  merely 
fanciful  comiparisons,  but  exact  ones — part  for  part;  and 
his  general  considerations  based  upon  these  comparisons  were 
of  a  brilliant  character. 


148  BIOLOGY   AND    ITS    MAKERS 

As  Huxley  has  said,  ''he  may  be  considered  as  the  founder 
of  the  modern  science  of  anatomy."  His  work  on  the  struc- 
ture of  the  brain  v/as  the  most  exact  which  had  appeared  up 
to  that  time,  and  in  his  studies  on  the  brain  he  entered  into 
broad  comparisons  as  he  had  done  in  the  study  of  the  other 
parts  of  the  animal  organization. 

He  died  at  the  age  of  forty-six,  without  being  able  to 
complete  a  large  work  on  human  anatomy,  illustrated  with 
colored  figures.  This  work  had  been  announced  and  en- 
tered upon,  but  only  that  part  relating  to  the  brain  had 
appeared  at  the  time  of  his  death.  Besides  drawings  of  the 
exterior  of  the  brain,  he  made  sections;  but  he  was  not  able 
to  determine  with  any  particular  degree  of  accuracy  the 
course  of  fiber  tracts  in  the  brain.  This  was  left  for  other 
workers.  He  added  many  new  facts  to  those  of  his  pred- 
ecessors, and  by  introducing  exact  comparisons  in  anatomy 
he  opened  the  field  for  Cuvier. 

Cuvier. — When  Cuvier,  near  the  close  of  the  eighteenth 
century,  committed  himself  definitely  to  the  progress  of 
natural  science,  he  found  vast  accumulations  of  separate 
mionographs  to  build  upon,  but  he  undertook  to  dissect 
representatives  of  all  the  groups  of  animals,  and  to  found 
his  comparative  anatomy  on  personal  observations.  The 
work  of  Vicq  d'Azyr  marked  the  highest  level  of  attain- 
ment, and  afforded  a  good  model  of  what  comparisons 
should  be;  but  Cuvier  had  even  larger  ideas  in  reference 
to  the  scope  of  comparative  anatomy  than  had  his  great 
predecessor. 

The  particular  feature  of  Cuvier's  service  was  that  in  his 
investigations  he  covered  the  whole  field  of  animal  organiza- 
tion from  the  lowest  to  the  highest,  and  uniting  his  results 
with  what  had  already  been  accomplished,  he  established 
comparative  anatomy  on  broad  lines  as  an  independent 
branch  of  natural  science.    Almost  at  the  outset  he  conceived 


RISE    OF    COMPARATIVE    ANATOMY  149 

the  idea  of  making  a  comprehensive  study  of  the  structure  of 
the  animal  kingdom.  It  was  fortunate  that  he  began  his 
investigations  with  thorough  work  upon  the  invertebrated 
animals;  for  from  this  view-point  there  was  gradually  un- 
folded to  his  great  mind  the  plan  of  organization  of  the  entire 
series  of  animals.  Not  only  is  a  knowledge  of  the  structure 
of  the  simplest  animals  an  essential  in  understanding  that  of 
the  more  modified  ones,  but  the  more  delicate  work  required 
in  dissecting  them  gives  invaluable  training  for  anatomizing 
those  of  more  complex  construction.  The  value  attached  to 
this  part  of  his  training  by  Cuvier  is  illustrated  by  the  advice 
that  he  gave  to  a  young  medical  student  w^ho  brought  to  his 
attention  a  supposed  discovery  in  anatomy.  "  Are  you  an 
entomologist  ?  "  inquired  Cuvier.  "  No,"  said  the  young  man. 
"Then,"  replied  Cuvier,  ''go  first  and  anatomize  an  insect, 
and  return  to  me;  and  if  you  still  believe  that  your  obser\^a- 
tions  are  discoveries  I  will  then  believe  you." 

Birth  and  Early  Education. — Cuvier  was  born  in  1769, 
at  Montbeliard,  a  village  at  that  tim^e  belonging  to  Wurttem- 
berg,  but  now  a  part  of  the  French  Jura.  His  father  was  a 
retired  militar}'  officer  of  the  Swiss  army,  and  the  family, 
being  Protestants,  had  moved  to  ^lontbeliard  for  freedom 
from  religious  persecution.  Cuvier  was  christened  Leopold- 
Christian-Frederic-Dagobert  Cuvier,  but  early  in  youth  took 
the  name  of  Georges  at  the  wish  of  his  mother,  who  had  lost 
an  infant  son  by  that  name. 

He  gave  an  early  promise  of  intellectual  leadership,  and 
his  mother,  although  not  well  educated,  took  the  greatest 
pains  in  seeing  that  he  formed  habits  of  industry  and  con- 
tinuous work,  hearing  him  recite  his  lessons  in  Latin  and 
other  branches,  although  she  did  not  possess  a  knovvledge  of 
Latin.  He  early  showed  a  leaning  toward  natural  history; 
having  access  to  the  v/orks  of  Cesner  and  Buffon,  he  profited 
by  reading  these  two  writers.     So  great  was  his  interest  that 


150  BIOLOGY    AND    ITS    MAKERS 

he  colored  the  plates  in  Buffon's  Natural  History  from  de- 
scriptions in  the  text. 

It  was  at  first  contemplated  by  his  family  that  he  should 
prepare  for  theology,  but  failing,  through  the  unfairness  of 
one  of  his  teachers,  to  get  an  appointment  to  the  theological 
seminary,  his  education  was  continued  in  other  directions. 
He  was  befriended  by  the  sister  of  the  Duke  of  Wurttemberg, 
who  sent  him  as  a  pensioner  to  the  famous  Carolinian  acad- 
emy at  Stuttgart.  There  he  showed  great  application,  and 
with  the  wonderful  memory  with  which  he  was  endowed,  he 
took  high  rank  as  a  student.  Here  he  met  Kielmeyer,  a 
young  instructor  only  four  years  older  than  himself,  who 
shared  his  taste  for  natural  history  and,  besides  this,  intro- 
duced him  to  anatomy.  In  after-years  Cuvier  acknowledged 
the  assistance  of  Kielmeyer  in  determining  his  future  work 
and  in  teaching  him  to  dissect. 

Life  at  the  Seashore. — In  1788  the  resources  of  his 
family,  which  had  always  been  slender,  became  further  re- 
duced by  the  inability  of  the  government  to  pay  his  father's 
retiring  stipend.  As  the  way  did  not  open  for  employ- 
ment in  other  directions,  young  Cuvier  took  the  post  of  in- 
structor of  the  only  son  in  the  family  of  Count  d'Hericy, 
and  went  with  the  family  to  the  sea-coast  in  Normandy, 
near  Caen.  For  six  years  (i  788-1 794)  he  lived  in  this  noble 
family,  with  much  time  at  his  disposal.  For  Cuvier  this 
period,  from  the  age  of  nineteen  to  twenty-five,  was  one  of 
constant  research  and  reflection. 

While  Paris  was  disrupted  by  the  reign  of  terror,  Cuvier, 
who,  although  of  French  descent,  regarded  himself  as  a  Ger- 
man, was  quietly  carrying  on  his  researches  into  the  struQure 
of  the  life  at  the  seaside.  These  years  of  diligent  study  and 
freedom  from  distractions  fixed  his  destiny.  Here  at  the 
sea-coast,  without  the  assistance  of  books  and  the  stimulus 
of  intercourse  with  other  naturalists,  he  was  drawn  directly 


RISE    OF    COMPARATIVE   ANATOMY  151 

to  nature,  and  through  his  great  industry  he  became  an  in- 
dependent observer.  Here  he  laid  the  foundation  of  his  ex- 
tensive knowledge  of  comparative  anatomy,  and  from  this 
quiet  spot  he  sent  forth  his  earliest  scientific  writings,  which 
served  to  carry  his  name  to  Paris,  the  great  center  of  scien- 
tific research  in  France, 

Goes  to  Paris. — His  removal  from  these  provincial  sur- 
roundings v.as  mainly  owing  to  the  warm  support  of  Tessier, 
who  was  spending  the  time  of  the  reign  of  terror  in  retirement 
in  an  adjacent  village,  under  an  assumed  name.  He  and 
Cu\'ier  met  in  a  scientific  society,  where  the  identity  of  Tessier 
was  discovered  by  Cuvier  on  account  of  his  ease  of  speech 
and  his  great  familiarity  with  the  topics  discussed.  A  friend- 
ship sprung  up  between  them,  and  Tessier  addressed  some 
of  his  scientific  friends  in  Paris  in  the  interest  of  Cuvier. 
By  this  powerful  introduction,  and  also  through  the  inter- 
vention of  Geoffroy  Saint-Hilaire,  he  came  to  Paris  in  1 795 
and  was  welcomed  into  the  group  of  working  naturalists 
at  the  Jardin  des  Plantes,  little  dreaming  at  the  time  that 
he  should  be  the  leader  of  the  group  of  men  gathered  around 
this  scientific  institution.  He  was  modest,  and  so  uncertain 
of  his  future  that  for  a  year  he  held  to  his  post  of  instructor, 
bringing  his  young  charge  with  him  to  Paris. 

Notwithstanding  the  doubt  which  he  entertained  regard- 
ing his  abilities,  his  career  proved  successful  from  the  begin- 
ning. In  Paris  he  entered  upon  a  brilliant  career,  which  was 
a  succession  of  triumphs.  His  unmistakable  talent,  com- 
bined with  industry  and  unusual  opportunities,  brought  him 
rapidly  to  the  front.  The  large  amount  of  material  already 
coll ec':ed,  and  the  stimulating  companionship  of  other  scien- 
tific workers,  afforded  an  environment  in  which  he  grew 
rapidly.  He  responded  to  the  stimulus,  and  developed  not 
only  into  a  great  naturalist,  but  expanded  into  a  finished 
gentleman  of  the  world.     Circumstances  shaped  themselves 


152  BIOLOGY   AND    ITS    MAKERS 

SO  that  he  was  called  to  occupy  prominent  offices  under  the 
government,  and  he  came  uhimately  to  be  the  head  of  the 
group  of  scientific  men  into  which  he  had  been  welcomed  as 
a  young  man  from  the  provinces. 

His  Physiognomy.— It  is  ver}^  interesting  to  note  in  his 
portraits  the  change  in  his  physiognomy  accompanying  his 
transformation  from  a  young  man  of  provincial  appearance 


Fig.  41. — CuviER  (1769-1832)  as  a  Young  Man. 

into  an  elegant  personage.  Fig.  41  shows  his  portrait  in  the 
early  days  when  he  was  less  mindful  of  his  personal  appear- 
ance. It  is  the  face  of  an  eager,  strong,  youzig  man,  still  re- 
taining traces  of  his  provincial  life.  His  long,  light-colored 
hair  is  unkempt,  but  does  not  hide  the  magnificent  propor- 
tions of  his  head.  Fig.  42  shows  the  growing  refinement  of 
features  which  came  with  his  advancement,  and  the  aristo- 
cratic look  of  supremacy  which  set  upon  his  countenance  after 


RISE    OF   COMPARATIVE   ANATOMY 


^53 


his  wide  recognition  passing  by  a  gradation  of  steps  from  the 
position  of  head  of  the  educational  system,  to  that  of  baron 
and  peer  of  France. 

Cuvier  was  a  man  of  commanding   power  and  colosal 


Fig.  42. — Cuvier  at  the  Zenith  of  His  Power. 


attainments ;  he  was  a  favorite  of  Napoleon  Bonaparte,  who 
elevated  him  to  office  and  made  him  director  of  the  higher 
educational  institutions  of  the  Empire.  But  to  whatever 
place  of  prominence  he  attained  in  the  government,  he  never 


154  BIOLOGY   AND    ITS    MAKERS 

lost  his  love  for  natural  science.  With  him  this  was  an 
absorbing  passion,  and  it  may  be  said  that  he  ranks  higher 
as  a  zoologist  than  as  a  legislator. 

Comprehensiveness  of  Mind. — Soon  after  his  arrival  in 
Paris  he  began  to  lecture  upon  comparative  anatomy  and  to 
continue  work  in  a  most  comprehensive  way  upon  the  subjects 
which  he  had  cultivated  at  Caen.  He  saw  ever}^thing  on  a 
large  scale.  This  led  to  his  making  extensive  studies  of  what- 
ever problems  engaged  his  mind,  and  his  studies  were  com- 
bined in  such  a  manner  as  to  give  a  broad  view  of  the  subject. 

Indeed,  comprehensiveness  of  mind  seems  to  have  been 
the  characteristic  which  most  impressed  those  who  were 
acquainted  with  him.  Flourens  says  of  him:  "  Ce  qui  ca- 
racterise  pariout  M.  Cuvier,  c'est  V esprit  vaster  His  broad 
and  comprehensive  mind  enabled  him  to  map  out  on  great 
lines  the  subject  of  comparative  anatomy.  His  breadth  was 
at  times  his  undoing,  for  it  must  be  confessed  that  when  the 
details  of  the  subject  are  considered,  he  was  often  inaccurate. 
This  was  possibly  owing  to  the  conditions  under  which  he 
worked;  having  his  mind  diverted  into  many  other  chan- 
nels, never  neglecting  his  state  duties,  it  is  reasonable  to 
suppose  that  he  lacked  the  necessary  time  to  prove  his  ob- 
servations in  anatomy,  and  we  may  in  this  way  account  for 
some  of  his  inaccuracies. 

Besides  being  at  fault  in  some  of  his  comparative  anat- 
omy, he  adhered  to  a  number  of  ideas  that  served  to  retard 
the  progress  of  science.  He  v/as  opposed  to  the  ideas  of  his 
contemporary  Lamarck,  on  the  evolution  of  animals.  He 
is  remembered  as  the  author  of  the  dogma  of  catastrophism 
in  geology.  He  adhered  to  the  old  notion  of  the  pre-forma- 
tion  of  the  embryo,  and  also  to  the  theory  of  the  sponta- 
neous origin  of  life. 

Founds  Comparative  Anatomy. — Regardless  of  this 
qualification,  he  was  a  great  and  distinguished  student,  and 


RISE    OF    COMPARATIVE    ANATOMY  1 55 

founded  comparative  anatomy.  From  1801  to  1805  appeared 
his  Legons  cTAnatomie  Comparec,  a  systematic  treatise  on  the 
comparative  anatomy  of  animals,  embracing  both  the  in- 
vertebrates and  the  vertebrates.  In  181 2  was  pubhshed  his 
great  work  on  the  fossil  bones  about  Paris,  an  achievement 
which  founded  the  science  of  vertebrate  palaeontology.  His 
extensive  examination  of  the  structure  of  fishes  also  added 
to  his  already  great  reputation.  His  book  on  the  animal 
kingdom  (Le  Regne  Animal  distrihue  d'apres  son  Organisa- 
tion, 1816),  in  which  he  expounded  his  type-theory,  has  been 
considered  in  a  previous  chapter. 

He  was  also  deeply  interested  in  the  historical  develop- 
ment of  science,  and  his  volumes  on  the  rise  of  the  natural 
sciences  give  us  almost  the  best  historical  estimate  of  the 
progress  of  science  that  we  have  at  the  present  day. 

His  Domestic  Life. — Mrs.  Lee,  in  a  chatty  account  of 
Cuvier,  shows  one  of  his  methods  of  work.  He  had  the 
faculty  of  making  others  assist  him  in  various  ways.  Not 
only  members  of  his  family,  but  also  guests  in  his  household 
were  pressed  into  service.  They  were  invited  to  examine 
different  editions  of  works  and  to  indicate  the  differences  in 
the  plates  and  in  the  text.  This  practice  resulted  in  saving 
much  time  for  Cuvier,  since  in  the  preparation  of  his  histor- 
ical lectures  he  undertook  to  examine  all  the  original  sources 
of  the  history  with  which  he  was  engaged.  In  his  lectures  he 
summarized  facts  relating  to  different  editions  of  books,  etc. 

Mrs.  Lee  also  gives  a  picture  of  his  family  life,  which  was, 
to  all  accounts,  very  beautiful.  He  was  devoted  to  his  wife 
and  children,  and  in  the  midst  of  exacting  cares  he  found 
time  to  bind  his  family  in  love  and  devotion.  Cuvier  was 
called  upon  to  suffer  poignant  grief  in  the  loss  of  his  chil- 
dren, and  his  direct  family  was  not  continued.  He  was 
especially  broken  by  the  death  of  his  daughter  who  had 
grown  to  young  womanhood  and  was  about  to  be  married. 


15^  BIOLOGY  AND   ITS   MAKERS 

From  the  standpoint  of  a  sincere  admirer,  Mrs.  Lee 
writes  of  his  generosity  and  nobility  of  temperament,  declar- 
ing that  his  career  demonstrated  that  his  mind  was  great 
and  free  from  both  envy  and  smallness. 

Some  Shortcomings. — Nevertheless,  there  are  certain 
things  in  the  life  of  Cuvier  that  we  wish  might  not  have  been. 
His  break  with  his  old  friends  Lamarck  and  Saint-Hilaire 
seems  to  show  a  domination  of  qualities  that  were  not  gen- 
erous and  kindly;  those  observations  of  Lamarck  showing  a 
much  profounder  insight  than  any  of  which  he  himself  was 
the  author  were  laughed  to  scorn.  His  famous  controversy 
with  Saint-Hilaire  marks  a  historical  moment  that  will  be 
dealt  with  in  the  chapter  on  Rise  of  Evolutionary  Thought. 

George  Bancroft,  the  American  historian,  met  him  during 
a  visit  to  Paris  in  1827.  He  speaks  of  his  magnificent  eyes 
and  his  fine  appearance,  but  on  the  whole  Cuvier  seems  to 
have  impressed  Bancroft  as  a  disagreeable  man. 

Some  of  his  shortcomings  that  served  to  retard  the  prog- 
ress of  science  have  been  mentioned.  Still,  with  all  his  faults, 
he  dominated  zoological  science  at  the  beginning  of  the  nine- 
teenth century,  and  so  powerful  was  his  influence  and  so  un- 
disputed was  his  authority  among  the  French  people  that 
the  rising  young  men  in  natural  science  sided  with  Cuvier 
even  when  he  was  wrong.  It  is  a  noteworthy  fact  that  France, 
under  the  influence  of  the  traditions  of  Cuvier,  was  the  last 
country  slowly  and  reluctantly  to  harbor  as  true  the  ideas 
regarding  the  evolution  of  animal  life. 

Cuvier's  Successors 

While  Cuvier's  theoretical  conclusions  exercised  a  retard- 
ing influence  upon  the  progress  of  biology,  his  practical 
studies  more  than  compensated  for  this.  It  has  been  pointed 
out  how  his  type-theory  led  to  the  reform  of  the  Linnaean 


RISE   OF   COMPARATIVE   ANATOMY 


157 


system,  but,  besides  this,  the  stimulus  which  his  investiga- 
tions gave  to  studies  in  comparative  anatomy  was  even  of 
more  beneficent  influence.  As  time  passed  the  importance 
of  comparative  anatomy  as  one  division  of  biological  science 
impressed  itself  more  and  more  upon  naturalists.  A  large 
number  of  investigators  in  France,  England,  and  Germany 
entered  the  field  and  took  up  the  work  where  Cuvier  had 


Fig.  43. — H.  Milne-Edwards,   1800-1885. 


left  it.  The  more  notable  of  these  successors  of  Cuvier 
should  come  under  consideration. 

His  intellectual  heirs  in  France  were  Milne-Edwards  and 
Lacaze-Duthiers. 

Milne-Edwards. — H.  Milne-Edwards  (1800-1885)  was  a 
man  of  great  industry  and  fine  attainments ;  prominent  alike 
in  comparative  anatomy,  comparative  physiology,  and  general 
zoolog}',  professor  for  many  years  at  the  Sorbonne  in  Paris. 


158  BIOLOGY   AND    ITS    MAKERS 

In  1827  he  introduced  into  biology  the  fruitful  idea  of  the  divi- 
sion of  physiological  labor.  He  completed  and  published 
excellent  researches  upon  the  structure  and  development  of 
many  animals,  notably  Crustacea,  corals,  etc.  His  Vvork  on 
comparative  anatomy  took  the  form  of  explanations  of  the 
activities  of  animals,  or  comparative  physiology.  His  com- 
prehensive treatise  Legons  sur  la  Physiologie  et  rAnaiomie 
Comparee,  in  fourteen  volumes,  185  7-1 881,  is  a  mine  of 
information  regarding  comparative  anatomy  as  v/ell  as  the 
physiology  of  organisms. 

Lacaze-Duthiers. — Henri  de  Lacaze-Duthiers  (1821- 
1901),  the  man  of  comprehensive  mind,  stimulating  as  an 
instructor  of  young  men,  inspiring  other  workers,  and  pro- 
ducing a  large  amount  of  original  research  on  his  own  ac- 
count, director  of  the  Seaside  Stations  atRoscoff  and  Banyuls, 
the  founder  of  a  noteworthy  periodical  of  experimental  zool- 
ogy— this  great  man,  whose  portrait  is  shown  in  Fig.  44,  was 
one  of  the  leading  comparative  anatomists  in  France. 

R.  Owen. — In  England  Richard  Owen  (1804-1892)  carried 
on  the  influence  of  Cuvier.  At  the  age  of  twenty-seven  he 
went  to  Paris  and  renewed  acquaintance  with  the  great  Cuvier, 
whom  he  had  met  the  previous  year  in  England.  He  spent 
some  time  at  the  Jardin  des  Plantes  examining  the  extensive 
collections  in  the  museum.  Although  the  idea  was  repudiated 
by  Owen  and  some  of  his  friends,  it  is  not  unlikely  that  the 
collections  of  fossil  animals  and  the  researches  upon  them 
which  engaged  Cuvier  at  that  time  had  great  influence  upon 
the  subsequent  studies  of  Ow^en.  Although  he  never  studied 
under  Cuvier,  in  a  sense  he  may  be  regarded  as  his  disciple. 
Owen  introduced  into  anatomy  the  important  conceptions 
of  analogy  and  homology,  the  former  being  a  likeness  based 
upon  the  use  to  which  organs  are  put,  as  the  wing  of  a  butter- 
fly and  the  wing  of  a  bat ;  while  homology  is  a  true  relation- 
ship founded  on  likeness  in  structure  and  development,  as 


RISE    OF    COMPARATIVE   ANATOMY 


159 


the  wing  of  a  bat  and  the  foreleg  of  a  dog.  i\nalogy  is  a 
superficial,  and  often  a  deceiving  relationship;  homology  is 
a  true  genetic  relationship.     It  is  obvious  that  this  distinction 


Fig.  44. — Lacaze-Duthiers,   1821-1901. 

is  of  great  importance  in  comparing  the  different  parts  of 
animals.  He  made  a  large  number  of  independent  discov- 
eries, and  published  a  monumental  work  on  the  comparative 


160 


BIOLOGY   AND   ITS   MAKERS 


anatomy  of  vertebrates  (1866-68).  In  much  of  his  thought 
he  was  singular,  and  many  of  his  general  conclusions  have 
not  stood  the  test  of  time.  He  undertook  to  establish  the 
idea  of  an  archtype  in  vertebrate  anatomy.  He  clung  to  the 
vertebral  theory  of  the  skull  long  after  Huxley  had  shown  such 
a  theory  to  be  untenable.     The  idea  that  the  skull  is  made  up 


Fig.  45. — Lorenzo  Oken,   1779-1851 


of  modified  vertebrae  was  propounded  by  Goethe  and  Oken. 
In  the  hands  of  Oken  it  became  one  of  the  anatomical  con- 
clusions of  the  school  of  Naturphilosophie.  This  school  of 
transcendental  philosophy  was  founded  by  Schelling,  and 
Oken  (Fig.  45)  was  one  of  its  typical  representatives.  The 
vertebral  theory  of  the  skull  was,  therefore,  not  original 
with  Owen,  but  he  adopted  it,  greatly  elaborated  it,  and 


RISE    OF    COMPARATIVE    ANATOMY 


i6l 


clung  to  it  blindly  long  after  the  foundations  upon  which  it 
rested  were  removed. 

Richard  Owen  (Fig.  46)  was  succeeded  by  Huxley  (1825- 
1895),  whose  exactness  of  observation  and  rare  judgment 


Fig.  46. — Richard  Owen,   1804-1892. 


as  to  the  main  facts  of  comparative  anatomy  mark  him  as 
one  of  the  leaders  in  this  field  of  research.  The  influence 
of  Huxley  as  a  popular  exponent  of  science  is  dealt  with 
in  a  later  chapter. 


l62  BIOLOGY   AND    ITS    MAKERS 

Meckel. — Just  as  Cuvier  stands  at  the  beginning  of  the 
school  of  comparative  anatomy  in  France,  so  does  J.  Fr. 
Meckel  in  Germany.  Meckel  (i  781-1833)  was  a  man  of 
rare  talent,  descended  from  a  family  of  distinguished  anat- 
omists. From  1804  to  1806  he  studied  in  Paris  under  Cuvier, 
and  when  he  came  to  leave  the  French  capital  to  become 
professor  of  anatomy  at  Halle,  he  carried  into  Germany  the 


Fig.  47. — J.  Fr.  Meckel,   i  781-1833. 

teachings  and  methods  of  his  master.  He  was  a  strong  force 
in  the  university,  attracting  students  to  his  department  by 
his  excellent  lectures  and  his  ability  to  arouse  enthusiasm. 
Some  of  these  students  were  stimulated  to  undertake  re- 
searches in  anatomy,  and  there  came  from  his  laboratory  a 
number  of  investigations  that  were  published  in  a  periodical 
which  he  founded.  Meckel  himself  produced  many  scientific 
papers  and  works  on  comparative  anatomy,  which  assisted 


RISE    OF    COMPARATIVE    ANATOMY  163 

materially  in  the  advancement  of  that  science.  His  portrait, 
which  is  rare,  is  shown  in  Fig.  47. 

Rathke. — Martin  Henry  Rathke  (i 793-1860)  greatly 
advanced  the  science  of  comparative  anatomy  by  insisting 
upon  the  importance  of  elucidating  anatomy  with  researches 
in  developmicnt.  This  is  such  an  important  consideration 
that  his  influence  upon  the  progress  of  comparative  anatomy 
can  not  be  overlooked.  After  being  a  professor  in  Dorpat, 
he  came,  in  1835,  to  occupy  the  position  of  professor  of  anat- 
omy and  zoology  at  Konigsberg,  which  had  been  vacated  by 
Von  Bacr  on  the  removal  of  the  latter  to  St.  Petersburg.  His 
writings  are  composed  with  great  intelligence,  and  his  facts 
are  carefully  coordinated.  Rathke  belonged  to  the  good  old 
school  of  German  writers  whose  researches  were  profound 
and  extensive,  and  whose  expression  was  clear,  being  based 
upon  matured  thought.  His  papers  on  the  aortic  arches 
and  the  Wolffian  body  are  those  most  commonly  referred  to 
at  the  present  time. 

Miiller. — Johannes  Miiller  (1801-1858),  that  phenomenal 
man,  besides  securing  recognition  as  the  greatest  physiol- 
ogist of  the  nineteenth  century,  also  gave  attention  to  com- 
parative anatomy,  and  earned  the  title  of  the  greatest  mor- 
phologist  of  his  time.  His  researches  were  so  accurate,  so 
complete,  so  discerning,  that  his  influence  upon  the  develop- 
ment of  comparative  anatomy  was  profound.  Although  he 
is  accorded,  in  history,  the  double  distinction  of  being  a  great 
anatomist  and  a  great  physiologist,  his  teaching  tended  to 
physiology;  and  most  of  his  distinguished  students  were 
physiologists  of  the  broadest  type,  uniting  comparative  anat- 
om.y  with  their  researches  upon  functional  activities.  (For 
Miiller's  portrait  see  p.  187.) 

Gegenbaur. — In  Karl  Gegenbaur  (i  826-1 903)  scientific 
anatomy  reached  its  highest  expression.  His  work  was  char- 
acterized by  broad  and  masterly  analysis  of  the  facts  of  strur- 


l64  BIOLOGY   AND    ITS    MAKERS 

ture,  to  which  were  added  the  ideas  derived  from  the  study  of 
the  development  of  organs.  He  was  endowed  with  an  intensely 
keen  insight,  an  insight  which  enabled  him  to  separate  from 
the  vast  mass  of  facts  the  important  and  essential  features, 
so  that  they  yielded  results  of  great  interest  and  of  lasting  im- 
portance.    This  gifted  anatomist  attracted  many  young  men 


Fig.  48. — Karl  Gegenbaur,  1826-1903. 

from  the  United  States  and  from  other  countries  to  pursue 
under  his  direction  the  study  of  comparative  anatomy.  He 
died  in  Heidelberg  in  1903,  where  he  had  been  for  many  years 
professor  of  anatomy  in  the  university. 

In  the  group  of  living  German  anatomists  the  names  of 
Furbringer,  Waldeyer,  and  Wiedersheim  can  not  go  unmen- 
tioned. 


RISE   OF   COMPARATIVE   ANATOMY  105 

E.  D.  Cope. — In  America  the  greatest  comparative 
anatomist  was  E.  D.  Cope  (1840-1897),  a  man  of  the  highest 
order  of  attainment,  who  dealt  with  the  comparative  anatomy 
not  only  of  living  forms,  but  of  fossil  life,  and  made  contribu- 
tions of  a  permanent  character  to  this  great  science;  a  man 
whose  title  to  distinction  in  the  field  of  com.parative  anatomy 
will  become  clearer  to  later  students  with  the  passage  of  time. 
For  Cope's  portrait  see  p.  336. 

Of  the  successors  of  Cuvier,  we  would  designate  Meckel, 
Owen,  Gegenbaur,  and  Cope  as  the  greatest. 

Comparative  anatomy  is  a  very  rich  subject,  and  when 
elucidated  by  embryology,  is  one  of  the  firm  foundations  of 
biology.  If  we  regard  anatomy  as  a  science  of  statics,  we 
recognize  that  it  should  be  united  with  physiology,  which 
represents  the  dynamical  side  of  life.  Comparative  anatomy 
and  comparative  physiology  should  go  hand  in  hand  in  the 
attempt  to  interpret  living  forms.  Advances  in  these  two 
subjects  embrace  nearly  all  our  knowledge  of  living  organisms. 
It  is  a  cause  for  congratulation  that  comparative  anatomy 
has  now  become  experimental,  and  that  gratifying  progress  is 
being  made  along  the  line  of  research  designated  as  experi- 
mental morphology.  Already  valuable  results  have  been 
attained  in  this  field,  and  the  outlook  of  experimental  mor- 
phology is  most  promising. 


CHAPTER  VIII 
BICHAT  AND  THE  BIRTH  OF  HISTOLOGY 

We  must  recognize  Bichat  as  one  of  the  foremost  men  in 
biological  histoiy,  although  his  name  is  not  well  known  to  the 
general  public,  nor  constantly  referred  to  by  biologists  as 
that  of  one  of  the  chief  luminaries  of  their  science.  In  him 
was  combined  extraordinary  talent  with  powers  of  intense 
and  prolonged  application;  a  combination  which  has  always 
produced  notable  results  in  the  world.  He  died  at  the  age 
of  thirty-one,  but,  within  a  productive  period  of  not  more 
than  seven  years,  he  made  observations  and  published  work 
that  created  an  epoch  and  made  a  lasting  impression  on  bio- 
logical history. 

His  researches  supplemented  those  of  Cuvier,  and  carried 
the  analysis  of  animal  organization  to  a  deeper  level.  Cuvier 
laid  the  foundations  of  comparative  anatomy  by  dissecting 
and  arranging  in  a  comprehensive  system  the  organs  of  ani- 
mals, but  Bichat  went  a  step  further  and  made  a  profound 
study  of  the  tissues  that  unite  to  make  up  the  organs.  As  we 
have  already  noted  in  a  previous  chapter,  this  was  a  step  in 
reaching  the  conception  of  the  real  organization  of  living 
beings. 

Buckle's  Estimate  of  Bichat. — It  is  interesting  to  note 
the  impression  made  by  Bichat  upon  one  of  the  greatest 
students  of  the  history  of  civilization.  Buckle  says  of  him: 
''Great,  however,  as  is  the  name  of  Cuvier,  a  greater  still 
remains  behind.     I  allude,  of  course,  to  Bichat,  whose  repu- 

166 


THE    BIRTH    OF    HISTOLOGY  167 

tation  is  steadily  advancing  as  our  knowledge  advances; 
who,  if  we  compare  the  shortness  of  his  life  with  the  reach  and 
depth  of  his  views,  must  be  pronounced  the  most  profound 
thinker  and  consummate  observer  by  whom  the  organization 
of  the  animal  frame  has  yet  been  studied. 

"We  may  except  Aristotle,  but  between  Aristotle  and 
Bichat  I  find  no  middle  man." 

Whether  or  not  we  agree  fully  with  this  panegyric  of 
Buckle,  we  must,  I  think,  place  Bichat  among  the  most  illus- 
trious men  of  biological  history,  as  Vesalius,  J.  Miiller,  Von 
Baer,  and  Balfour. 

Marie  Francois  Xavier  Bichat  was  born  in  1771  at 
Thoirette,  department  of  the  Ain.  His  father,  who  was  a 
physician,  directed  the  early  education  of  his  son  and  had 
the  satisfaction  of  seeing  him  take  kindly  to  intellectual  pur- 
suits. The  young  student  was  distinguished  in  Latin  and 
mathematics,  and  showed  early  a  fondness  for  natural  his- 
tory. Having  elected  to  follow  the  calling  of  his  father,  he 
went  to  Lyons  to  study  medicine,  and  came  under  the 
instruction  of  Petit  in  surgery. 

Bichat  in  Paris. — It  was,  on  the  whole,  a  fortunate  cir- 
cumstance for  Bichat  that  the  turbulent  events  of  the  French 
Revolution  drove  him  from  Lyons  to  Paris,  where  he  could 
have  the  best  training,  the  greatest  stimulus  for  his  growth, 
and  at  the  same  time  the  widest  field  for  the  exercise  of  his 
talents.  We  find  him  in  Paris  in  1793,  studying  under  the 
great  surgeon  Desault. 

He  attracted  attention  to  himself  in  the  class  of  this  dis- 
tinguished teacher  and  operator  by  an  extemporaneous  report 
on  one  of  the  lectures.  It  was  the  custom  in  Desault's  classes 
to  have  the  lectures  of  the  professor  reported  upon  before  an 
assistant  by  some  student  especially  appointed  for  the  pur- 
pose. On  one  occasion  the  student  who  had  been  appointed 
to  prepare  and  deliver  the  review  was  absent,  and  Bichat, 


l68  BIOLOGY    AND    ITS    MAKERS 

who  was  gifted  v/ith  a  powerful  memory,  vohmteered  without 
previous  notice  to  take  his  place.  The  lecture  was  a  long  and 
difficult  one  on  the  fractures  of  the  clavicle,  but  Bichat's 
abstract  was  so  clear,  forceful,  and  complete  that  its  delivery 
in  well-chosen  language  produced  a  great  sensation  both  upon 
the  instructor  and  the  students.  This  notable  performance 
served  to  bring  him  directly  to  the  attention  of  Desault,  who 
invited  him  to  become  his  assistant  and  to  live  in  his  family. 
The  association  of  Bichat  with  the  great  surgeon  was  most 
happy.  Desault  treated  him  as  a  son,  and  when  he  suddenly 
died  in  1795,  the  care  of  preparing  his  works  for  the  printer 
was  left  to  Bichat. 

The  fidelity  with  which  Bichat  executed  this  trust  was 
characteristic  of  his  noble  nature.  He  laid  aside  his  own 
personal  interests,  and  his  researches  in  which  he  was  already 
immersed,  and  by  almost  superhuman  labor  completed  the 
fourth  volume  of  Desault's  Journal  oj  Surgery  and  at  the 
same  time  collected  and  published  his  scattered  papers.  To 
these  he  added  observations  of  his  ov/n,  making  alterations 
to  bring  the  work  up  to  the  highest  plane.  Thus  he  paid 
the  debt  of  gratitude  which  he  felt  he  owed  to  Desault  for 
his  friendship  and  assistance. 

In  1797  he  was  appointed  professor  of  anatomy,  at  the 
age  of  twenty-six,  and  from  then  to  the  end  of  his  life,  in  1801, 
he  continued  in  his  career  of  remarkable  industry. 

The  portrait  of  this  very  attractive  man  is  shown  in 
Fig.  49.  His  face  shows  strong  intellectuality.  He  is  de- 
scribed as  of  "  middling  stature,  with  an  agreeable  face  lighted 
by  piercing  and  expressive  eyes."  He  was  much  beloved  by 
his  students  and  associates,  being  "in  all  relations  of  life 
most  amiable,  a  stranger  to  envy  or  other  hateful  passions, 
modest  in  demeanor  and  lively  in  his  manners,  which  were 
open  and  free." 

His  Phenomenal  Industry. — His  industry  was  phenom- 


THE    BIRTH    OF    HISTOLOGY  169 

enal;  besides  doing  the  work  of  a  professor,  he  attended  to 
a  considerable  practice,  and  during  a  single  winter  he  is  said 
to  have  examined  with  care  six  hundred  bodies  in  the  pur- 
suance of  his  researches  upon  pathological  anatomy. 


Fig.  49. — BicHAT,   1771-1801. 

In  the  year  1800,  when  he  was  thirty  years  old,  began  to 
appear  the  results  of  his  matured  researches.  We  speak  of 
these  as  being  matured,  not  on  account  of  his  age  or  the  great 
number  of  years  he  had  labored  upon  them,  but  from  the 


lyo  BIOLOGY   AND    ITS   MAKERS 

intensity  and  completeness  with  which  he  had  pursued  his 
investigations,  thus  giving  to  his  work  a  lasting  quality. 

First  came  his  treatise  on  the  membranes  {Traite  des 
Membranes))  followed  quickly  by  his  Physiological  Re- 
searches into  the  Phenomena  of  Life  and  Death  (Recherches 
Physiologiques  sur  la  Vie  et  la  Mort);  then  appeared  his 
General  Anatomy  {Anatomie  Generak)  in  1801,  and  his  trea- 
tise upon  Descriptive  Anatomy,  upon  which  he  was  working 
at  the  time  of  his  death. 

His  death  occurred  in  i8ci,  and  was  due  partly  to  an 
accident.  He  slipped  upon  the  stairs  of  the  dissecting-room, 
and  his  fall  was  followed  by  gastric  derangement,  from  which 
he  died. 

Results  of  His  Work. — ^The  new  science  of  the  anatomy 
of  the  tissues  which  he  founded  is  now  known  as  histology, 
and  the  general  anatomy,  as  he  called  it,  has  now  become 
the  study  of  minute  anatomy  of  the  tissues.  Bichat  studied 
the  membranes  or  tissues  very  profoundly,  but  he  did  not 
employ  the  microscope  and  make  sketches  of  their  cellular 
construction.  The  result  of  his  work  was  to  set  the  world 
studying  the  minute  structure  of  the  tissues,  a  consequence 
of  which  led  to  the  modern  study  of  histology.  Since  this 
science  was  constructed  directly  upon  his  foundation,  it  is 
proper  to  recognize  him  as  the  founder  of  histology. 

Carpenter  says  of  him :  "Altogether  Bichat  left  an  impress 
upon  the  science  of  life,  the  depth  of  which  can  scarcely  be 
overrated;  and  this  not  so  much  by  the  facts  which  he  col- 
lected and  generalized,  as  by  the  method  of  inquiry  which 
he  developed,  and  by  the  systematic  form  which  he  gave  to 
the  study  of  general  anatomy  in  its  relations  both  to  physi- 
ology and  pathology." 

Bichat's  More  Notable  Successors. — ^His  influence  ex- 
tended far,  and  after  the  establishment  of  the  cell-theory 
took  on  a  new  phase.     Microscopic  study  of  the  tissues  has 


THE    BIRTH    OF    HISTOLOGY  I?! 

now  become  a  separate  division  of  the  science  of  anatomy, 
and  engages  the  attention  of  a  very  large  number  of  workers. 
While  the  men  who  built  upon  Bichat's  foundation  are  nu- 
merous, we  shall  select  for  especial  mention  only  a  few  of  the 
more  notable,  as  Schwann,  Koelliker,  Schultze,  Virchov/, 
Leydig,  and  Ramon  y  Cajal,  whose  researches  stand  in  the 
direct  Hne  of  development  of  the  ideas  promulgated  by 
Bichat. 

Schwann. — Schwann's  cell-theory  was  the  result  of  close 
attention  to  the  microscopic  structure  of  the  tissues  of  ani- 
mals. It  was  an  extension  of  the  knowledge  of  the  tissues 
which  Bichat  distinguished  and  so  thoroughly  investigated 
from  other  points  of  view.  The  cell-theory,  which  took  rise 
in  1839,  was  itself  epoch-making,  and  the  science  of  general 
anatomy  was  influenced  by  it  as  deeply  as  was  the  science  of 
embryology.  The  leading  founder  of  this  theory  was 
Theodor  Schwann,  whose  portrait  is  shown  on  page  245, 
where  there  is  also  a  more  extended  account  of  his  labors  in 
connection  with  the  cell-theory.  Had  not  the  life  of  Bichat 
been  cut  off  in  his  early  manhood,  he  might  well  have  lived 
to  see  this  great  discovery  added  to  his  own. 

Koelliker. — ^Albrecht  von  Koelliker  (181 7-1905)  was  one 
of  the  greatest  histologists  of  the  nineteenth  century.  He  is  a 
striking  figure  in  the  development  of  biology  in  a  general  way, 
distinguished  as  an  embryologist,  as  a  histologist,  and  in 
other  connections.  During  his  long  life,  from  181 7  to  1905, 
he  made  an  astounding  number  of  additions  to  our  knowledge 
of  microscopic  anatomy.  In  the  early  years  of  his  scientific 
activity,  ^'he  helped  in  establishing  the  cell-theory,  he  traced 
the  origin  of  tissues  from  the  segmenting  ovum  through  the 
developing  embryo,  he  demonstrated  the  continuity  between 
nerve-fibers  and  nerve-cells  of  vertebrates  (1845),  •  •  •  ^^^ 
much  more."  He  is  mentioned  further,  in  connection  with 
the  rise  of  embryology,  in  Chapter  X. 


172  BIOLOGY    AND    ITS    MAKERS 

The  strong  features  of  this  veteran  of  research  are  shown 
in  the  portrait,  Fig.  50,  which  represents  him  at  the  age  of 
seventy. 

In  1847  h^  was  called  to  the  University  of  Wiirzburg, 
where  he  remained  to  the  time  of  his  death.  From  1850  to 
1900,  scarcely  a  year  passed  without  some  important  contri- 
bution from  Von  Koelliker  extending  the  knowledge  of  his- 
tology. His  famous  text-book  on  the  structure  of  the  tissues 
(Handbuch  der  Gewehelehre)  passed  through  six  editions  from 
1852  to  1893,  the  final  edition  of  it  being  worked  over  and 
brought  up  to  date  by  this  extraordinary  man  after  he  had 
passed  the  age  of  seventy-five.  By  workers  in  biology  this 
will  be  recognized  as  a  colossal  task.  In  the  second  volume 
of  the  last  edition  of  this  work,  which  appeared  in  1893,  he 
went  completely  over  the  ground  of  the  vast  accumulation  of 
information  regarding  the  nerv^ous  system  which  an  army  of 
gifted  and  energetic  workers  had  produced.  This  was  all 
thoroughly  digested,  and  his  histological  work  brought  down 
to  date. 

Schultze. — The  fine  observations  of  Max  Schultze  (1825- 
1874)  may  also  be  grouped  with  those  of  the  histologists. 
We  shall  have  occasion  to  speak  of  him.  more  particularly  in 
the  chapter  on  Protoplasm..  He  did  memorable  ser\ace  for 
general  biology  in  establishing  the  protoplasm  doctrine,  but 
many  of  his  scientific  memoirs  are  in  the  line  of  normal 
histology ;  as,  those  on  the  structure  of  the  olfactory  mem- 
brane, on  the  retina  of  the  eye,  the  muscle  elements,  the 
nerves,  etc.,  etc. 

Normal  Histology  and  Pathology. — But  histology  has 
two  phases:  the  investigation  of  the  tissues  in  health,  which 
is  called  normal  histology;  and  the  study  of  the  tissues  in 
disease  and  under  abnormal  conditions  of  development, 
which  is  designated  pathological  histology.  The  latter  divi- 
sion, on  account  of  its  importance  to  the  medical  man,  has 


Fig.  50. — Von  Koelliker,   1817-1905. 


174  BIOLOGY   AND    ITS    MAKERS 

been  extensively  cultivated,  and  the  development  of  patho- 
logical study  has  greatly  extended  the  knowledge  of  the 
tissues  and  has  had  its  influence  upon  the  progress  of  normal 
histology.  Goodsir,  in  England,  and  Henle,  in  Germany, 
entered  the  lield  of  pathological  histology,  both  doing  work 


Fig.  51. — Rudolph  Virchow,   1821-1903. 

of  historical  importance.  They  were  soon  followed  b}-  Vir- 
chow, whose  eminence  as  a  man  and  a  scientist  has  made 
his  name  familiar  to  people  in  general. 

Virchow. — Rudolph  Virchow  (1821-1903),  for  many 
years  a  professor  in  the  University  of  Berlin,  was  a  notable 
man  in  biological  science  and  also  as  a  member  of  the  German 


THE    BIRTH    OF    HISTOLOGY  175 

parliament.  He  assisted  in  molding  the  cell-theory  into 
better  form,  and  in  1858  published  a  work  on  Cellular 
Pathology,  which  applied  the  cell-theory  to  diseased  tissues. 
It  is  to  be  remembered  that  Bichat  was  a  medical  man,  in- 
tensely interested  in  pathological,  or  diseased,  tissues,  and  we 


Fig.  52. — Franz  Leydig,  1821-1908. 
Courtesy  of  Dr.  Wm.  M.  Wheeler. 

see  in  Virchow  the  one  who  especially  extended  Bichat's  work 
on  the  side  of  abnormal  histology.  Virchow's  name  is  asso- 
ciated also  with  the  beginning  of  the  idea  of  germinal  conti- 
nuity, which  is  the  basis  of  Ijiological  ideas  regarding  hered- 
ity (see,  further.  Chapter  XV). 

Leydig. — Franz  Leydig  (Fig.  52)  was  early  in  the  field 
as  a  histologist  with  his  handbook  {Lehrhuch  der  Histologie 


176 


BIOLOGY   AND    ITS    MAKERS 


des  Menschen  mid  der  Thiere)  published  in  1857.  He  applied 
histology  especially  to  the  tissues  of  insects  in  1864  and  sub- 
sequent years,  an  account  of  which  has  already  been  given 
in  Chapter  V. 

Cajal  as  Histologist. — Ramon  y  Cajal,  professor  in  the 
University  of  Madrid,  is  a  histologist  whose  work  in  a  special 


Fig,  53. — S.  Ramon  y  Cajal,  1850- 


field  of  research  is  of  world-wide  renown.  His  investigations 
into  the  microscopic  texture  of  the  nervous  system  and  sense- 
organs  have  in  large  part  cleared  up  the  questions  of  the  com- 
plicated relations  between  the  nervous  elements.  In  com- 
pany with  other  European  investigators  he  visited  the  United 
States  in  1899  on  the  invitation  of  Clark  University,  where  his 
lectures  were  a  feature  of  the  celebration  of  the  tenth  anni- 


THE    BIRTH    OF    HISTOLOGY  177 

versary  of  that  university.  Besides  receiving  many  honors  in 
previous  years,  in  1906  he  was  awarded,  in  conjunction  with 
the  Italian  histologist  Golgi,  one  of  the  Nobel  prizes  in  recog- 
nition of  his  notable  investigations.  Golgi  invented  the  stain- 
ing methods  that  Ramon  y  Cajal  has  applied  so  extensively 
and  so  successfully  to  the  histology  of  the  nervous  system. 

These  men  in  particular  may  be  remembered  as  the  inves- 
tigators who  expanded  the  work  of  Bichat  on  the  tissues: 
Schwann,  for  disclosing  the  microscopic  elements  of  animal 
tissues  and  founding  the  cell-theory;  Koclliker,  as  the  typical 
histologist  after  the  analysis  of  tissues  into  their  elementary 
parts;  Virchow,  as  extending  the  cell-idea  to  abnormal  his- 
tology; Leydig,  for  applying  histology  to  the  lower  animals ; 
and  Ramon  y  Cajal,  for  investigations  into  the  histology  of 
the  nervous  system. 

Text-Books  of  Histology. — ^Besides  the  works  mentioned, 
the  text-books  of  Frey,  Strieker,  Ranvier,  Klein,  Schafer, 
and  others  represent  a  period  in  the  general  introduction  of 
histology  to  students  between  1859  and  1885.  But  these 
excellent  text-books  have  been  largely  superseded  by  the 
more  recent  ones  of  Stohr,  Boem-Davidoff,  Piersol,  Szy- 
monowicz,  and  others.  The  number  of  living  investigators 
in  histology  is  enormous;  and  their  work  in  the  subject  of 
cell-structure  and  in  the  department  of  embryology  now 
overlaps. 

In  pathological  histology  may  be  observed  an  illustration 
of  the  application  of  biological  studies  to  medicine.  While 
no  attempt  is  made  to  give  an  account  of  these  practical  ap- 
plications, they  are  of  too  great  importance  to  go  unmen- 
tioned.  Histological  methods  are  in  constant  use  in  clinical 
diagnosis,  as  in  blood  counts,  the  study  of  inflammations,  of 
the  action  of  phagocytes,  and  of  all  manner  of  abnormal 
growths. 

In  attempting  to  trace  the  beginning  of  a  definite  founda- 


178  BIOLOGY   AND    ITS    MAKERS 

tion  for  the  work  on  the  structure  of  tissues,  we  go  back  to 
Bichat  rather  than  to  Leeuwenhoek,  as  Richardson  has  pro- 
posed. Bichat  was  the  first  to  give  a  scientific  basis  for 
histology  founded  on  extensive  observations,  since  all  earlier 
observers  gave  only  separated  accounts  of  the  structure  of 
particular  tissues. 


CHAPTER  IX 

THE  RISE  OF  PHYSIOLOGY 
Harvey    Haller    Johannes  Muller 

Physiology  had  a  parallel  development  with  anatomy, 
but  for  convenience  it  will  be  considered  separately.  Anatomy 
shows  us  that  animals  and  plants  are  wonderfully  con- 
structed, but  after  we  understand  their  architecture  and  even 
their  minute  structure,  the  questions  remain,  What  are  all 
the  organs  and  tissues  for  ?  and  what  takes  place  within  the 
parts  that  are  actually  alive  ?  Physiology  attempts  to  answer 
questions  of  this  nature.  It  stands,  therefore,  in  contrast 
with  anatomy,  and  is  supplementary  to  it.  The  activities  of 
living  organisms  are  varied,  and  depend  on  life  for  their 
manifestations.  These  manifestations  may  be  called  vital 
activities.     Physiology  embraces  a  study  of  them  all. 

Physiology  of  the  Ancients. — ^This  subject  began  to  at- 
tract the  attention  of  ancient  medical  men  who  wished  to 
fathom  the  activities  of  the  body  in  order  to  heal  its  diseases, 
but  it  is  such  a  difficult  thing  to  begin  to  comprehend  the 
activities  of  life  that  even  the  simpler  relationships  were  im- 
perfectly understood,  and  they  resorted  to  mythical  explana- 
tions. They  spoke  of  spirits  and  humors  in  the  body  as 
causes  of  various  changes;  the  arteries  were  supposed  to 
can-y  air,  the  veins  only  blood ;  and  nothing  was  known  of  the 
circulation.  There  arose  among  these  early  medical  men 
the  idea  that  the  body  was  dominated  by  a  subtle  spirit. 
This  went  under  the  name  pneuma,  and  the  pneuma-theory 
held  sway  until  the  period  of  the  Revival  of  Learning. 

179 


l8o  BIOLOGY   AND    ITS   MAKERS 

Among  the  ancient  physiologists  the  great  Roman  phy- 
sician Galen  is  the  most  noteworthy  figure.  As  he  was  the 
greatest  anatomist,  so  he  was  also  the  greatest  physiologist 
of  ancient  times.  All  physiological  knowledge  of  the  time 
centered  in  his  wTitings,  and  these  were  the  standards  of 
physiology  for  many  centuries,  as  they  were  also  for  anatomy. 
In  the  early  days  anatomy,  physiology,  and  medicine  were  all 
united  into  a  poorly  digested  mass  of  facts  and  fancies.  This 
state  of  affairs  lasted  until  the  sixteenth  century,  and  then  the 
awakening  came,  through  the  efforts  of  gifted  men,  endued 
with  the  spirit  of  independent  investigation.  The  advances 
made  depended  upon  the  work  or  leadership  of  these  men, 
and  there  are  certain  periods  of  especial  importance  for  the 
advance  of  physiology  that  must  be  pointed  out. 

Period  of  Harvey. — ^The  first  of  these  epochs  to  be  espe- 
cially noted  here  is  the  period  of  Harvey  (15 78- 165 7).  In  his 
time  the  old  idea  of  spirits  and  humors  was  giving  way,  but 
there  was  still  much  vagueness  regarding  the  activities  of  the 
body.  He  helped  to  illuminate  the  subject  by  showing  a  con- 
nection between  arteries  and  veins,  and  by  demonstrating 
the  circulation  of  the  blood.  As  we  have  seen  in  an  earlier 
chapter,  Harvey  did  not  observe  the  blood  passing  through 
the  capillaries  from  arteries  to  veins,  but  his  reasoning  was 
unassailable  that  such  a  connection  must  exist,  and  that  the 
blood  made  a  complete  circulation.  He  gave  his  conclusions 
in  his  medical  lectures  as  early  as  1619,  but  did  not  publish 
his  views  until  1628.  It  was  reserved  for  Malpighi,  in  1661, 
actually  to  see  the  circulation  through  the  capillaries  under 
the  microscope,  and  for  Leeuwenhoek,  in  1669  and  later 
years,  to  extend  these  observations. 

It  was  during  Harvey's  life  that  the  microscope  vras 
brought  into  use  and  was  of  such  great  assistance  in  advanc- 
ing knowledge.  Harvey  himself,  however,  made  little  use 
of  this  instrument.     It  was  during  his  life  also  that  the  knowl- 


THE    RISE    OF    PHYSIOLOGY  l8l 

edge  of  development  was  greatly  promoted,  first  through  his 
own  efforts,  and  later  through  those  of  Malpighi. 

Harvey  is  to  be  recognized,  then,  as  the  father  of  modem 
physiology.  Indeed,  before  his  time  physiology  as  such  can 
hardly  be  spoken  of  as  having  come  into  existence.  He  intro- 
duced experimental  work  into  physiology,  and  thus  laid  the 
foundation  of  modem  investigation.  It  was  the  method  of 
Harvey  that  made  definite  progress  in  this  line  possible,  and 
accordingly  we  honor  him  as  one  of  the  greatest  as  well  as 
the  earliest  of  physiologists. 

Period  of  Haller.^From  Harvey's  time  we  pass  to  the 
period  of  Haller  (i 708-1 777),  at  the  beginning  of  which 
physiology  was  still  wrapped  up  with  medicine  and  anatomy. 
The  great  work  of  Haller  was  to  create  an  independent  science 
of  physiology.  He  made  it  a  subject  to  be  studied  for  its 
own  sake,  and  not  merely  as  an  adjunct  to  medicine.  Haller 
was  a  man  of  vast  and  varied  leaming,  and  to  him  was  applied 
by  unsympathetic  critics  the  title  of  "  that  abyss  of  leaming.'* 
His  portrait,  as  shown  in  Fig.  54,  gives  the  impression  of 
a  somewhat  pompous  and  overbearing  personality.  He 
was  egotistical,  self-complacent,  and  possessed  of  great 
self-esteem.  The  assurance  in  the  inerrancy  of  his  own 
conclusions  was  a  marked  characteristic  of  Haller's  mind. 
While  he  was  a  good  observer,  his  own  work  showing  con- 
scientious care  in  observation,  he  was  not  a  good  interpreter, 
and  we  are  to  recollect  that  he  vigorously  opposed  the  idea 
of  development  set  forth  by  Wolff,  and  we  must  also  recog- 
nize that  his  researches  formed  the  chief  starting-point  of  an 
erroneous  conception  of  vitality. 

As  Verwom  points  out,  Haller's  own  experiments  upon 
the  phenomena  of  irritability  were  exact,  but  they  were 
misinterpreted  by  his  followers,  and  through  the  molding 
influence  of  others  the  attempted  explanation  of  their  mean- 
ing grew  into  the  conception  of  a  special  vital  force  belong- 


l82 


BIOLOGY   AND    ITS    MAKERS 


ing  to  living  organisms  only.  In  its  most  complete  form, 
this  idea  provided  for  a  distinct  dualism  between  living  and 
lifeless  matter,  making  all  vital  actions  dependent  upon  the 


Fig.  54. — Albrecht  Haller,   i 708-1 777. 


operation  of  a  mystical  supernatural  agency.  This  assump- 
tion removed  vital  phenomena  from  the  domain  of  clear 
scientific  analysis,  and  for  a  long  time  exercised  a  retarding 
influence  upon  the  progress  of  physiology. 


THE    RISE    OF    PHYSIOLOGY  183 

His  chief  service  of  permanent  value  was  that  he  brought 
into  one  work  all  the  facts  and  the  chief  theories  of  physiology 
carefully  arranged  and  digested.  This,  as  has  been  said, 
made  physiology  an  independent  branch  of  science,  to  be 
pursued  for  itself  and  not  merely  as  an  adjunct  to  the  study 
of  medicine.  The  work  referred  to  is  his  Elements  of  Physi- 
ology {Elementa  Physiologice  Corporis  Humani,  1758),  one 
of  the  noteworthy  books  marking  a  distinct  epoch  in  the 
progress  of  science. 

To  the  period  of  Haller  also  belongs  the  discovery  of 
oxygen,  in  1774,  by  Priestley,  a  discovery  which  was  destined 
to  have  profound  influence  upon  the  subsequent  development 
of  physiology,  so  that  even  now  physiology  consists  largely 
in  tracing  the  way  in  which  oxygen  enters  the  body,  the 
manner  in  which  it  is  distributed  to  the  tissues,  and  the  vari- 
ous phases  of  vital  activity  that  it  brings  about  within  the 
living  tissues. 

Charles  Bell.— The  period  of  Haller  may  be  considered 
as  extending  beyond  his  lifetime  and  as  terminating  when  the 
influence  of  Muller  began  to  be  felt.  Another  discovery  com- 
ing in  the  closing  years  of  Haller's  period  marks  a  capital 
advance  in  physiology.  I  refer  to  the  discovery  of  Charles 
Bell  (i 774-1842)  showing  that  the  nerve  iibers  of  the  anterior 
roots  of  the  spinal  cord  belong  to  the  motor  type,  while  those 
of  the  posterior  roots  belong  to  the  sensor)^  type. 

This  great  truth  was  arrived  at  theoretically,  rather  than 
as  the  result  of  experimental  demonstration.  It  was  first  ex- 
pounded by  Bell  in  181 1  in  a  small  essay  entitled  Idea  of  a 
New  Anatomy  of  the  Brain,  which  was  printed  for  private 
distribution.  It  was  expanded  in  his  papers,  beginning  in 
1821,  and  published  in  the  Philosophical  Transactions  of 
the  Royal  Society  of  London,  and  finally  embodied  in  his 
work  on  the  nervous  system,  published  in  1830.  At  this 
latter  date  Johannes  Muller  had  reached  the  age  of  twenty- 


1^4  BIOLOGY   AND    ITS    MAKERS 

nine,  and  had  already  entered  upon  his  career  as  the  lead- 
ing physiologist  of  Germany.  What  Bell  had  divined  he 
demonstrated  by  experiments. 

Charles  Bell  (Fig.  55)  was  a  surgeon  of  eminence;  in 
private  life  he  was  distinguished  by  "  unpretending  amenity, 
and  simplicity  of  manners  and  deportment.'' 


Fig.  55. — Charles  Bell,   1774-1842. 

Period  of  Johannes  Miiller. — The  period  that  marks  the 
beginning  of  modern  physiology  came  next,  and  was  due  to 
the  genius  and  force  of  Johannes  Miiller  (i 801-1858).  Ver- 
wom  says  of  him:  "He  is  one  of  those  monumental  fig- 
ures that  the  history  of  every  science  brings  forth  but  orxe. 


THE    RISE    OF    PHYSIOLOGY  185 

They  change  the  whole  aspect  of  the  field  in  which  they  work, 
and  all  later  growth  is  influenced  by  their  labors."  Johannes 
MuUer  was  a  man  of  very  unusual  talent  and  attainments, 
the  possessor  of  a  master  mind.  Some  have  said,  and  not 
without  reason,  that  there  was  something  supernatural  about 
Mliller,  for  his  whole  appearance  bore  the  stamp  of  the  un- 
common. His  portrait,  with  its  massive  head  above  the  broad 
shoulders,  is  shown  in  Fig.  56.  In  his  lectures  his  manner 
and  his  gestures  reminded  one  of  a  Catholic  priest.  Early  in 
his  life,  before  the  disposition  to  devote  himself  to  science 
became  so  overwhelming,  he  thought  of  entering  the  priest- 
hood, and  there  clung  to  him  all  his  life  some  marks  of 
the  holy  profession.  In  his  highly  intellectual  face  we  find 
''a  trace  of  severity  in  his  mouth  and  compressed  lips,  with 
the  expression  of  most  earnest  thought  on  his  brow  and  eyes, 
and  with  the  remembrance  of  a  finished  work  in  every 
wrinkle  of  his  countenance." 

This  extraordinary  man  exercised  a  profound  influence 
upon  those  who  came  into  contact  with  him.  He  excited 
almost  unbounded  enthusiasm  and  great  veneration  among 
his  students.  They  were  allowed  to  work  close  by  his  side, 
and  so  magnetic  was  his  personality  that  he  stimulated  them 
powerfully  and  succeeded  in  transmitting  to  them  some 
of  his  own  mental  qualities.  As  professor  of  physiology  in 
Berlin,  MuUer  trained  many  gifted  young  men,  among  whom 
were  Briicke  (1819-1892),  Du  Bois-Reymond  (1818-1896), 
and  Helmholtz  (1821-1894),  who  became  distinguished 
scholars  and  professors  in  German  universities.  Helmholtz, 
speaking  of  MuUer's  influence  on  students,  paid  this  tribute 
to  the  grandeur  of  his  teacher:  "Whoever  comes  into  contact 
with  men  of  the  first  rank  has  an  altered  scale  of  values  in  life. 
Such  intellectual  contact  is  the  most  interesting  event  that 
life  can  offer." 

The  particular  service  of  Johannes  Miiller  to  science  was 


l86  BIOLOGY   AND    ITS    MAKERS 

to  make  physiology  broadly  comparative.  So  comprehensive 
was  his  grasp  upon  the  subject  that  he  gained  for  himself 
the  title  of  the  greatest  physiologist  of  modem  times.  He 
brought  together  in  his  great  work  on  the  physiology  of  man 
not  only  all  that  had  been  previously  made  known,  carefully 
sifted  and  digested,  but  a  great  mass  of  new  information, 
which  was  the  result  of  his  own  investigations  and  of  those 
of  his  students.  So  rigorous  were  his  scientific  standards 
that  he  did  not  admit  into  this  treatise  anything  which  had 
been  untested  either  by  himself  or  by  some  of  his  assistants 
or  students.  Verworn  says  of  this  monumental  work,  which 
appeared  in  1833,  under  the  title  Handbuch  der  Physiologie 
des  Menschen:  "This  work  stands  to-day  unsurpassed  in 
the  genuinely  philosophical  manner  in  which  the  material, 
swollen  to  vast  proportions  by  innumerable  special  researches, 
was  for  the  first  time  sifted  and  elaborated  into  a  unitary 
picture  of  the  mechanism  within  the  living  organism.  In  this 
respect  the  Handbuch  is  to-day  not  only  unsurpassed,  but 
unequalled." 

Miiller  was  the  most  accurate  of  observers;  indeed,  he  is 
the  most  conspicuous  example  in  the  nineteenth  century  of  a 
man  who  accomplished  a  prodigious  amount  of  work  all  of 
which  was  of  the  highest  quality.  In  physiology  he  stood  on 
broader  lines  than  had  ever  been  used  before.  He  employed 
every  means  at  his  command — experimenting,  the  obser\^a- 
tion  of  simple  animals,  the  microscope,  the  discoveries  in 
physics,  in  chemistry,  and  in  psychology. 

He  also  introduced  into  physiology  the  pnnciples  of  psy- 
chology, and  it  is  from  the  period  of  Johannes  Miiller  that 
we  are  to  associate  recognition  of  the  close  connection  be- 
tween the  operations  of  the  mind  and  the  physiology  of  the 
brain  that  has  come  to  occupy  such  a  conspicuous  position 
at  the  present  time. 

Miiller  died  in  1858,  having  reached  the  age  of  fifty -seven, 


Fig.  56. — Johannes  Muller,   1801-1858. 


i^S  BIOLOGY   AND    ITS   MAKERS 

but  his  influence  was  prolonged  through  the  teachings  of  his 
students. 

Physiology  after  Muller. 

Ludwig.— Among  the  men  who  handed  on  the  torch  of 
Muller,  Ludwig  (Fig.  57)  must  be  mentioned.     Although 


Fig.   57.— Ludwig,   1816-1895. 


he  was  never  a  pupil  of  Muller,  he  gathered  stimulus  from 
his  writings  and  researches.  For  many  years  he  lectured 
in  the  University  of  Leipsic,  attracting  to  that  university 
high-minded,  eager,  and  gifted  young  men,  who  received 


THE   RISE   OF  PHYSIOLOGY 


189 


from  this  great  luminary  of  physiology  by  expression  what 
he  himself  had  derived  from  contact  with  Mtiller  and  his 
writings.  There  are  to-day  distributed  through  the  univer- 
sities a  number  of  young  physiologists  who  stand  only  one 


Fig.  58. — Du  Bois-Reymond,  1818-1896. 

generation  removed  from  Johannes  Miiller,  and  who  still 
labor  in  the  spirit  that  was  introduced  into  this  depart- 
ment of  study  by  that  great  master. 

Du  Bois-Reymond. — Du  Bois-Reymond  (Fig.  58),  an- 
other of  his  distinguished  pupils,  came  to  occupy  the  chair 


IQO  BIOLOGY   AND    ITS    MAKERS 

which  Mliller  himself  had  filled  in  the  University  of  Berlin, 
and  during  the  period  of  his  vigor  was  in  physiology  one  of 
the  lights  of  the  world.  It  is  no  uncommon  thing  to  find 
recently  published  physiologies  dedicated  either  to  the  mem- 
ory of  Johannes  MuUer,  as  in  the  case  of  that  remarkable 
General  Physiology  by  Verworn ;  or  to  Ludwig,  or  to  Du 
Bois-Reymond,  who  were  in  part  his  intellectual  product. 
From  this  disposition  among  physiologists  to  do  homage  to 
Miiller,  we  are  able  to  estim^ate  somewhat  more  closely  the 
tremendous  reach  of  his  influence. 

Bernard. — ^When  Miiller  was  twelve  years  old  there  was 
born  in  Saint- Julien,  department  of  the  Rhone,  Claude 
Bernard,  who  attained  an  eminence  as  a  physiologist,  of  which 
the  French  nation  are  justly  proud.  Although  he  was  little 
thought  of  as  a  student,  nevertheless  after  he  came  under  the 
influence  of  Magendie,  at  the  age  of  twenty-six,  he  developed 
rapidly  and  showed  his  true  metal.  He  exhibited  great 
manual  dexterity  in  performing  experiments,  and  also  a 
luminous  quality  of  mind  in  interpreting  his  observations. 
One  of  his  greatest  achievements  in  physiology  was  the  dis- 
covery of  the  formation  within  the  liver  of  glycogen,  a  sub- 
stance chemically  related  to  sugar.  Later  he  discovered  the 
system  of  vaso-motor  nerves  that  control  and  regulate  the 
caliber  of  the  blood-vessels.  Both  of  these  discoveries  as- 
sisted materially  in  understanding  the  wonderful  changes 
that  are  going  on  within  the  human  body.  But  besides  his 
technical  researches,  any  special  consideration  of  which  lies 
quite  beyond  the  purpose  of  this  book,  he  published  in  1878- 
1879  a  work  upon  the  phenomena  of  life  in  animals  and 
vegetables,  a  work  that  had  general  influence  in  extending 
the  knowledge  of  vital  activities.  I  refer  to  his  now  classic 
Legons  sur  les  Phenomenes  de  la  vie  communs  aux  animaux  et 
aux  vegetaux. 

The  thoughtful  face  of  Bernard  is  shown  in  his  portrait^ 


THE    RISE    OF    PHYSIOLOGY  191 

Fig.  59.  He  was  one  of  those  retiring,  silent  men  whose 
natures  are  difficult  to  fathom,  and  who  are  so  frequently 
misunderstood.  A  domestic  infelicity,  that  led  to  the  separa- 
tion of  himself  from  his  family,  added  to  his  isolation  and 
loneliness.     When  touched  by  the  social  spirit  he  charmed 


Fig.  59. — Claude  Bernard,   1813-1878. 

people  by  his  personality.  He  was  admired  by  the  Emperor 
Napoleon  Third,  through  whose  influence  Bernard  acquired 
two  fine  laboratories.  In  1868  he  was  elected  to  the 
French  Academy,  and  became  thereby  one  of  the  "Forty 
Immortals." 

Foster  describes  him  thus:  "Tall  in  stature,  with  a  fine 


192  BIOLOGY   AND    ITS    MAKERS 

presence,  with  a  noble  head,  the  eyes  full  at  once  of  thought 
and  kindness,  he  drew  the  look  of  observers  upon  him  wher- 
ever he  appeared.  As  he  walked  in  the  streets  passers-by 
might  be  heard  to  say  '  I  wonder  who  that  is ;  he  must  be 
some  distinguished  man.'  " 

Two  Directions  of  Growth. — Physiology,  established  on 
the  broad  foundations  of  Muller,  developed  along  two  inde- 
pendent pathways,  the  physical  and  the  chemical.  We  find 
a  group  of  physiologists,  among  whom  Weber,  Ludwig, 
Du  Bois-Reymond,  and  Helmholtz  were  noteworthy  leaders, 
devoted  to  the  investigations  of  physiological  facts  through 
the  application  of  measurements  and  records  made  by  ma- 
chinery. With  these  men  came  into  use  the  time-markers,  the 
myographs,  and  the  ingenious  methods  of  recording  blood- 
pressure,  changes  in  respiration,  the  responses  of  muscle  and 
nerve  to  various  forms  of  stimulation,  the  rate  of  transmission 
of  nerve-currents,  etc. 

The  investigation  of  vital  activities  by  means  of  measure- 
ments and  instrumental  records  has  come  to  represent  one 
especial  phase  of  modern  physiolog}' .  As  might  have  been 
predicted,  the  discoveries  and  extensions  of  knowledge  re- 
sulting from  this  kind  of  experimentation  have  been  remark- 
able, since  it  is  obvious  that  permanent  records  made  by 
mechanical  devices  will  rule  out  many  errors;  and,  moreover, 
they  afford  an  opportunity  to  study  at  leisure  phenomena 
that  occupy  a  very  brief  time. 

The  other  marked  line  of  physiological  investigation  has 
been  in  the  domain  of  chemistry,  where  Wohler,  Liebig, 
Kuhne,  and  others  have,  through  the  study  of  the  chemical 
changes  occurring  in  its  body,  observed  the  various  activities 
that  take  place  within  the  organism.  They  have  reduced  all 
tissues  and  all  parts  of  the  body  to  chemical  analysis,  studied 
the  chemical  changes  in  digestion,  in  respiration,  etc.  The 
more  recent  observ^ers  have  also  made  a  particular  feature  of 


THE    RISE    OF    PHYSIOLOGY  193 

the  study  of  the  chemical  changes  going  on  within  the  living 
matter. 

The  union  of  these  two  chief  tendencies  into  the  physico- 
chemical  aspects  of  physiology  has  established  the  modem 
way  of  looking  upon  vital  activities.  These  vital  activi- 
ties are  now  regarded  as  being,  in  their  ultimate  analysis, 
due  to  physical  and  chemical  changes  taking  place  within  the 
living  substratum.  All  along,  this  physico-chemical  idea  has 
been  in  contest  with  that  of  a  duality  between  the  body  and 
the  life  that  is  manifested  in  it.  The  vitalists,  then,  have  had 
many  controversies  with  those  who  make  their  interpretations 
along  physico-chemical  lines.  We  will  recollect  that  vitalism 
in  the  hands  of  the  immediate  successors  of  Haller  became 
not  only  highly  speculative,  but  highly  mystical,  tending  to 
obscure  any  close  analysis  of  vital  activity  and  throwing 
explanations  all  back  into  the  domain  of  mysticism.  Johannes 
Miiller  was  also  a  vitalist,  but  his  vitalism  was  of  a  more 
acceptable  form.  He  thought  of  changes  in  the  body  as 
being  due  to  vitality — to  a  living  force;  but  he  did  not  deny 
the  possibility  of  the  transformation  of  this  vital  energy  into 
other  forms  of  energy ;  and  upon  the  basis  of  Miiller's  work 
there  has  been  built  up  the  modem  conception  that  there  is 
found  in  the  human  body  a  particular  transformation-form 
of  energy,  not  a  mystical  vital  force  that  presides  over  all 
manifestations  of  life. 

The  advances  in  physiology,  beginning  with  those  of 
William  Harvey,  have  had  immense  influence  not  only  upon 
medicine,  but  upon  all  biology.  We  find  now  the  successful 
and  happy  union  between  physiology  and  morphology  in  the 
work  which  is  being  so  assiduously  carried  on  to-day  under 
the  title  of  experimental  morphology. 

The  great  names  in  physiology  since  Muller  are  numerous, 
and  perhaps  it  is  invidious  to  mention  particular  ones;  but, 
inasmuch  as  Ludwig  and  Du  Bois-Reymond  have  been 
13 


194  BIOLOGY   AND    ITS    MAKERS 

spoken  of,  we  may  associate  with  them  the  names  of  Sir 
Michael  Foster  and  Burdon- Sanderson,  in  England ;  and  of 
Briicke  (one  of  Muller's  disciples)  and  Verworn,  in  Ger- 
many, as  modern  leaders  whose  investigations  have  pro- 
moted advance,  and  whose  clear  exposition  of  the  facts  and 
the  theories  of  physiology  have  added  much  to  the  dignity 
of  the  science. 


CHAPTER  X 

VON  BAER  AND  THE  RISE  OF  EMBRYOLOGY 

Anatomy  investigates  the  arrangement  of  organic  tissues ; 
embryology,  or  the  science  of  development,  shows  how  they 
are  produced  and  arranged.  There  is  no  more  fascinating 
division  of  biological  study.  As  Minot  says:  "Indeed,  the 
stories  which  embryology  has  to  tell  are  the  most  romantic 
known  to  us,  and  the  wildest  imaginative  creations  of  Scott 
or  Dumas  are  less  startling  than  the  innumerable  and  almost 
incredible  shifts  of  role  and  change  of  character  which 
embryology  has  to  entertain  us  with  in  her  histories." 

Embiyology  is  one  of  the  most  important  biological  sci- 
ences in  furnishing  clues  to  the  past  history  of  animals. 
Every  organism  above  the  very  lowest,  no  matter  how  com- 
plex, begins  its  existence  as  a  single  microscopic  cell,  and 
between  that  simple  state  and  the  fully  formed  condition 
every  gradation  of  structure  is  exhibited.  Every  time  an 
animal  is  developed  these  constructive  changes  are  repeated 
in  orderly  sequence,  and  one  who  studies  the  series  of  steps 
in  development  is  led  to  recognize  that  the  process  of 
building  an  animal's  body  is  one  of  the  most  wonderful 
in  all  nature. 

Rudimentary  Organs.— But,  strangely  enough,  the  course 
of  development  in  any  higher  organism  is  not  straightforward, 
but  devious.  Instead  of  organs  being  produced  in  the  most 
direct  manner,  unexpected  by-paths  are  followed,  as  when 
all  higher  animals  acquire  gill-clefts  and  many  other  rudi- 

195 


19^  BIOLOGY    AND    ITS    MAKERS 

mentary  organs  not  adapted  to  their  condition  of  life.  Most 
of  the  rudimentary  organs  are  transitory,  and  bear  testimony, 
as  hereditary  survivals,  to  the  line  of  ancestry.  They  are 
clues  by  means  of  which  phases  in  the  evolution  of  animal 
life  may  be  deciphered. 

Bearing  in  mind  the  continually  shifting  changes  through 
which  animals  pass  in  their  embryonic  development,  one 
begins  to  see  why  the  adult  structures  of  animals  are  so  diffi- 
cult to  understand.  They  are  not  only  complex ;  they  are  also 
greatly  modified.  The  adult  condition  of  any  organ  or  tissue 
is  the  last  step  in  a  series  of  gradually  acquired  modifications, 
and  is,  therefore,  the  farthest  departure  from  that  which  is 
ancestral  and  archetypal.  But  in  the  process  of  formation 
all  the  simpler  conditions  are  exhibited.  If,  therefore,  we 
wish  to  understand  an  organ  or  an  animal,  we  must  follow  its 
development,  and  see  it  in  simpler  conditions,  before  the 
great  modifications  have  been  added. 

The  tracing  of  the  stages  whereby  cells  merge  into  tissues, 
tissues  into  organs,  and  determining  how  the  organs  by  com- 
binations build  up  the  body,  is  embryology.  On  account  of 
the  extended  applications  of  this  subject  in  biology,  and  the 
light  which  it  throws  on  all  structural  studies,  we  shall  be 
justified  in  giving  its  history  at  somewhat  greater  length 
than  that  adopted  in  treating  of  other  topics. 

Five  Historical  Periods. — The  story  of  the  rise  of  this 
interesting  department  of  biology  can,  for  convenience,  be 
divided  into  five  periods,  each  marked  by  an  advance  in 
general  knowledge.  These  are:  (i)  the  period  of  Harvey 
and  Malpighi;  (2)  the  period  of  Wolff;  (3)  the  period  of 
Von  Baer;  (4)  the  period  from  Von  Baer  to  Balfour;  and 
(5)  the  period  of  Balfour,  with  an  indication  of  present  tend- 
encies. Among  all  the  leaders  Von  Baer  stands  as  a  monu- 
mental figure  at  the  parting  of  the  ways  between  the  new 
and  the  old — the  sane  thinker,  the  great  observer. 


THE    RISE    OF    EMBRYOLOGY  197 

The  Period  of  Harvey  and  Malpighi 

In  General.— The  usual  account  of  the  rise  of  embryol- 
ogy is  derived  from  German  writers.  But  there  is  reason  to 
depart  from  their  traditions,  in  which  Wolff  is  heralded  as  its 
founder,  and  the  one  central  figure  prior  to  Pander  and 
Von  Baer. 

The  embryological  work  of  Wolff's  great  predecessors, 
Harv^ey  and  Malpighi,  has  been  passed  over  too  lightly. 
Although  these  men  have  received  ample  recognition  in 
closely  related  fields  of  investigation,  their  insight  into  those 
mysterious  events  that  culminate  in  the  formation  of  a  new 
animal  has  been  rarely  appreciated.  Now  and  then  a  few 
writers,  as  Brooks  and  Whitman,  have  pointed  out  the  great 
worth  of  Harvey's  work  in  embryology,  but  fewer  have 
spoken  for  Malpighi  in  this  connection.  Koelliker,  it  is  true, 
in  his  address  at  the  unveiling  of  the  statue  of  Malpighi,  in 
his  native  town  of  Crevalcuore,  in  1894,  gives  him  well- 
merited  recognition  as  the  founder  of  embryology,  and  the 
late  Sir  Michael  Foster  has  written  in  a  similar  vein  in  his 
delightful  Lectures  on  the  History  oj  Physiology. 

However  great  was  Harvey's  work  in  embryology,  I  ven- 
ture to  say  that  Maipighi's  was  greater  when  considered  as  a 
piece  of  observation.  Harvey's  v/ork  is  more  philosophical; 
he  discusses  the  nature  of  development,  and  shows  unusual 
powers  as  an  accurate  reasoner.  But  that  part  of  his  treatise 
devoted  to  observation  is  far  less  extensive  and  exact  than 
Maipighi's,  and  throughout  his  lengthy  discussions  he  has 
the  flavor  of  the  ancients. 

Maipighi's  work,  on  the  contrary,  flavors  more  of  the 
modems.  In  terse  descriptions,  and  with  many  sketches,  he 
shows  the  changes  in  the  hen's  egg  from  the  close  of  the  first 
day  of  development  onward. 

It  is  a  noteworthy  fact  that,  at  the  period  in  which  he 


19^  BIOLOGY   AND    ITS    MAKERS 

lived,  Malpighi  could  so  successfully  curb  the  tendency  to 
indulge  in  wordy  disquisitions,  and  that  he  was  satisfied  to 
observe  carefully,  and  tell  his  story  in  a  simple  way.  This 
quality  of  mind  is  rare.  As  Emerson  has  said:  "I  am  im- 
pressed with  the  fact  that  the  greatest  thing  a  human  soul 
ever  does  in  this  world  is  to  see  something,  and  tell  what  it 
saw  in  a  plain  way.  Hundreds  of  people  can  talk  for  one 
who  can  think,  but  thousands  can  think  for  one  who  can  see. 
To  see  clearly  is  poetry,  philosophy,  and  religion  all  in  one." 
But  ''to  see "  here  means,  of  course,  to  interpret  as  well  as 
to  observe. 

Although  there  were  observers  in  the  field  of  embryology 
before  Harvey,  little  of  substantial  value  had  been  produced. 
The  earliest  attempts  were  vague  and  uncritical,  embracing 
only  fragmentary  views  of  the  more  obvious  features  of  body- 
formation.  Nor,  indeed,  should  we  look  for  much  advance 
in  the  field  of  embryology  even  in  Harvey's  time.  The  reason 
for  this  w^ill  become  obvious  when  we  remember  that  the 
renewal  of  independent  observation  had  just  been  brought 
about  in  the  preceding  century  by  Vesalius,  and  that  Harvey 
himself  was  one  of  the  pioneers  in  the  intellectual  awakening. 
Studies  on  the  development  of  the  body  are  specialized, 
involving  observations  on  minute  structures  and  recondite 
processes,  and  must,  therefore,  wait  upon  considerable  ad- 
vances in  anatomy  and  physiology.  Accordingly,  the  science 
of  embryology  was  of  late  development. 

Harvey. — Harvey's  was  the  first  attempt  to  make  a  criti- 
cal analysis  of  the  process  of  development,  and  that  he  did  not 
attain  more  was  not  owing  to  limitations  of  his  powers  of  dis- 
cernment, but  to  the  necessity  of  building  on  the  general  level 
of  the  science  of  his  time,  and,  further,  to  his  lack  of  instru- 
ments of  observation  and  technique.  Nevertheless,  Harvey 
may  be  considered  as  having  made  the  first  independent 
advance  in  embryology. 


THE  RISE    OF    EMBRYOLOGY  199 

By  clearly  teaching,  on  the  basis  of  his  own  observations, 
the  gradual  formation  of  the  body  by  aggregation  of  its  parts, 
he  anticipated  Wolff.  This  doctrine  came  to  be  known  under 
the  title  of  "epigenesis,"  but  Harv^ey's  epigenesis*  was  not, 
as  Wolff's  was,  directed  against  a  theory  of  pre-delineation  of 
the  parts  of  the  embryo,  but  against  the  ideas  of  the  medical 
men  of  the  time  regarding  the  metamorphosis  of  germinal 
elements.  It  lacked,  therefore,  the  dramatic  setting  which 
surrounded  the  work  of  Wolff  in  the  next  century.  Had  the 
doctrine  of  pre-formation  been  current  in  Harvey's  time,  we 
are  quite  justified  in  assuming  that  he  would  have  assailed  it 
as  vigorously  as  did  Wolff. 

His  Treatise  on  Generation.— Harvey's  embiyological 
work  was  published  in  1651  under  the  title  Exercitationes  de 
Generaiione  Animalium.  It  embraces  not  only  observations 
on  the  development  of  the  chick,  but  also  on  the  deer  and  some 
other  mammals.  As  he  was  the  court  physician  of  Charles  I, 
that  sovereign  had  many  deer  killed  in  the  park,  at  interv^als, 
in  order  to  give  Harvey  the  opportunity  to  study  their  devel- 
opment. 

As  fruits  of  his  observation  on  the  chick,  he  showed  the 
position  in  which  the  embryo  arises  within  the  egg,  viz.,  in 
the  white  opaque  spot  or  cicatricula;  and  he  also  corrected 
Aristotle,  Fabricius,  and  his  other  predecessors  in  many  par- 
ticulars. 

Harvey's  greatest  predecessor  in  this  field,  Fabricius,  was 
also  his  teacher.  When,  in  search  of  the  best  training  in 
medicine,  Harvey  took  his  way  from  England  to  Italy,  as 
already  recounted,  he  came  under  the  instruction  of  Fa- 
bricius in  Padua.  In  160c,  Fabricius  published  sketches 
showing  the  development  of  animals;  and,  again,  in  1625, 
six  years  after  his  death,  appeared  his  illustrated  treatise  on 

*  As  Whitman  has  pointed  out,  Aristotle  taught  epigenesis  as  clearly  as 
Harvey,  and  is,  therefore,  to  be  regarded  as  the  founder  of  that  conception. 


200  BIOLOGY   AND    ITS    MAKERS 

the  development  of  the  chick.  Except  the  figures  of  Coiter 
(1573),  those  of  Fabricius  were  the  earliest  published  illus- 
trations of  the  kind.  Altogether  his  figures  show  develop- 
mental stages  of  the  cow,  sheep,  pig,  galeus,  serpent,  rat,  and 
chick. 

Harvey's  own  treatise  was  not  illustrated.  With  that 
singular  independence  of  mind  for  which  he  was  conspicuous, 
the  vision  of  the  pupil  was  not  hampered  by  the  authority  of 
his  teacher,  and,  trusting  only  to  his  own  sure  observation 
and  reason,  he  described  the  stages  of  development  as  he 
saw  them  in  the  egg,  and  placed  his  own  construction  on 
the  facts. 

One  of  the  earliest  activities  to  arrest  his  attention  in  the 
chick  was  a  pulsating  point,  the  heart,  and,  from  this  observa- 
tion, he  supposed  that  the  heart  and  the  blood  were  the  first 
formations.  He  says:  "But  as  soon  as  the  egg,  under  the 
influence  of  the  gentle  warmth  of  the  incubating  hen,  or  of 
warmth  derived  from  another  source,  begins  to  pullulate, 
this  spot  forthwith  dilates,  and  expands  like  the  pupil  of  the 
eye;  and  from  thence,  as  the  grand  center  of  the  egg,  the 
latent  plastic  force  breaks  forth  and  germinates.  This  first 
commencement  of  the  chick,  however,  so  far  as  I  am  aware,, 
has  not  yet  been  observed  by  any  one." 

It  is  to  be  understood,  however,  that  the  descriptive  part 
of  his  treatise  is  relatively  brief  (about  40  pages  out  of  350  in 
Willis's  translation),  and  that  the  bulk  of  the  106  ''  exercises  " 
into  which  his  work  is  divided  is  devoted  to  comments  on  the 
older  writers  and  to  discussions  of  the  nature  of  the  process 
of  development. 

The  aphorism, "  omne  vivum  ex  ovo,'''  though  not  invented 
by  Harvey,  was  brought  into  general  use  through  his  wTitings. 
As  used  in  his  day,  however,  it  did  not  have  its  full  modern 
significance.  With  Harvey  it  meant  simply  that  the  embr}^os 
of  all  animals,  the  viviparous  as  well  as  the  oviparous,  orig- 


Fig.  6o. —  Frontispiece  to  Harvey's  Generatione  Animalium  (165 1). 


202  BIOLOGY   AND    ITS    MAKERS 

nate  in  eggs,  and  it  was  directed  against  certain  contrary 
medical  theories  of  the  time. 

The  first  edition  of  his  Generatione  Animalium,  London, 
1 65 1,  is  provided  with  an  allegorical  frontispiece  embodying 
this  idea.  As  shown  in  Fig.  60,  it  represents  Jove  on  a 
pedestal,  uncovering  a  round  box,  or  ovum,  bearing  the 
inscription  ^'  ex  ovo  omnia,''^  and  from  the  box  issue  all  forms 
of  living  creatures,  including  also  man. 

Malpighi. — ^The  observer  in  embryology  who  looms  into 
prominence  between  Harvey  and  Wolff  is  Malpighi.  He 
supplied  what  was  greatly  needed  at  the  time — an  illustrated 
account  of  the  actual  stages  in  the  development  of  the  chick 
from  the  end  of  the  first  day  to  hatching,  shorn  of  verbose 
references  and  speculations. 

His  observations  on  development  are  in  two  separate 
memoirs,  both  sent  to  the  Royal  Society  in  1672,  and  pub- 
lished by  the  Society  in  Latin,  under  the  titles  De  Formatione 
Pulli  in  Ovo  and  De  Ovo  Incuhato.  The  two  taken  together 
are  illustrated  by  twelve  plates  containing  eighty-six  figures, 
and  the  twenty-two  quarto  pages  of  text  are  nearly  all  devoted 
to  descriptions,  a  marked  contrast  to  the  350  pages  of  Harvey 
unprovided  with  illustrations. 

His  pictures,  although  not  correct  in  all  particulars,  repre- 
sent what  he  was  able  to  see,  and  are  very^  remarkable  for 
the  age  in  which  they  were  made,  and  considering  the  instru- 
ments of  observation  at  his  command.  They  show  successive 
stages  from  the  time  the  embryo  is  first  outlined,  and,  taken 
in  their  entirety,  they  cover  a  wide  range  of  stages. 

His  observations  on  the  development  of  the  heart,  com- 
prising twenty  figures,  are  the  most  complete.  He  clearly 
illustrates  the  aortic  arches,  those  transitory  structures  of 
such  great  interest  as  showing  a  phase  in  ancestral  history. 

He  was  also  the  first  to  show  by  pictures  the  formation  of 
the  head-fold  and  the  neural  groove,  as  well  as  the  brain- 


Fig.  6i. — Selected     Sketches    from    Malpighi's    Works,    Showing 
Stages  in  the  Development  of  the  Chick  (1672). 


204 


BIOLOGY    AND    ITS    MAKERS 


vesicles  and  eye-pockets.  His  delineation  of  heart,  brain, 
and  eye-vesicles  are  far  ahead  of  those  illustrating  Wolff's 
Tlieoria  Generationis,  made  nearly  a  hundred  years  later. 

Fig.  6i  shows  a  few  selected  sketches  from  the  various 
plates  of  his  embryological  treatises,  to  compare  with  those  of 
Wolff.     (See  Fig.  63.) 

The  original  drawings  for  De  Ovo  Inctibato,  still  in  pos- 
session of  the  Royal  Society,  are  made  in  pencil  and  red  chalk, 


Fig.  62. — Marcello  Malpighi,   1628--1694. 

and  an  examination  of  them  shows  that  they  far  surpass  the 
reproductions  in  finish  and  accuracy. 

While  Harvey  taught  the  gradual  formation  of  parts, 
Malpighi,  from  his  own  observations,  supposed  the  rudiments 


THE    RISE    OF    EMBRYOLOGY  205 

of  the  embryo  to  pre-exist  within  the  egg.  He  thought  that, 
possibly,  the  blood-vessels  were  in  the  form  of  tubes,  closely 
Avrapped  together,  which  by  becoming  filled  with  blood  were 
distended.  Nevertheless,  in  the  treatises  mentioned  above 
he  is  very  temperate  in  his  expressions  on  the  whole  matter, 
and  evidently  believed  in  the  new  formation  of  many  parts. 

The  portrait  of  Malpighi  shown  in  Fig.  62  is  taken  from 
his  life  by  Atti.  From  descriptions  of  his  personal  appear- 
ance (see  page  58)  one  would  think  that  this  is  probably  a 
better  likeness  than  the  strikingly  handsome  portrait  painted 
by  Tabor,  and  presented  by  Malpighi  to  the  Royal  Society 
of  London.     For  a  reproduction  of  the  latter  see  page  59. 

Malpighi*s  Rank. — On  the  whole,  Malpighi  should  rank 
above  Harvey  as  an  embryologist,  on  account  of  his  dis- 
coveries and  fuller  representation,  by  drawings  and  descrip- 
tions, of  the  process  of  development.  As  Sir  Michael  Foster 
has  said:  "The  first  adequate  description  of  the  long  series 
of  changes  by  which,  as  they  melt  the  one  into  the  other, 
like  dissolving  views,  the  little  white  opaque  spot  in  the  egg 
is  transformed  into  the  feathered,  living,  active  bird,  was 
given  by  Malpighi.  And  where  he  left  it,  so  for  the  most 
part  the  matter  remained  until  even  the  present  century. 
For  this  reason  we  may  speak  of  him  as  the  founder  of 
embryology." 

The  Period  of  Wolff 

Between  Harvey  and  Wolff,  embryology  had  become 
dominated  by  the  theory  that  the  embryo  exists  already 
pre-formed  within  the  egg,  and,  as  a  result  of  the  rise  of  this 
new  doctrine,  the  publications  of  Wolff  had  a  different  setting 
from  that  of  any  of  his  predecessors.  It  is  only  fair  to  say 
that  to  this  circumstance  is  owing,  in  large  part,  the  prom- 
inence of  his  name  in  connection  with  the  theory  of  epigenesis. 


2o6,  BIOLOGY   AND    ITS    MAKERS 

As  we  have  already  seen,  Harvey,  more  than  a  century  before 
the  publications  of  Wolff,  had  clearly  taught  that  develop- 
ment is  a  process  of  gradual  becoming.  Nevertheless,  Wolff's 
work,  as  opposed  to  the  new  theory,  was  very  important. 

While  the  facts  fail  to  support  the  contention  that  he  was 
the  founder  of  epigenesis,  it  is  to  be  remembered  that  he  has 
claims  in  other  directions  to  rank  as  the  foremost  student  of 
embryology  prior  to  Von  Baer. 

As  a  preliminary  to  discussing  Wolff's  position,  we  should 
bring  under  consideration  the  doctrine  of  pre-formation  and 
encasement. 

Rise  of  the  Theory  of  Pre-delineation. — The  idea  of  pre- 
formation in  its  first  form  is  easily  set  forth.  Just  as  when 
we  examine  a  seed  we  find  within  an  embryo  plantlet,  so  it 
was  supposed  that  the  various  forms  of  animal  life  existed 
in  miniature  within  the  egg.  The  process  of  development 
was  supposed  to  consist  of  the  expansion  or  unfolding  of  this 
pre-formed  embryo.  The  process  was  commonly  illustrated 
by  reference  to  flower-buds.  '^  Just  as  already  in  a  small  bud 
all  the  parts  of  the  flower,  such  as  stamens  and  colored  petals, 
are  enveloped  by  the  green  and  still  undeveloped  sepals; 
just  as  the  parts  grow  in  concealment  and  then  suddenly 
expand  into  a  blossom,  so  also  in  the  development  of  animals, 
it  was  thought  that  the  already  present,  small  but  transparent 
parts  grow,  gradually  expand,  and  become  discernible." 
(Hertwig.)  From  the  feature  of  unfolding  this  was  called 
in  the  eighteenth  century  the  theory  of  evolution,  giving  to 
that  term  quite  a  different  meaning  from  that  attached  to  it 
at  the  present  time. 

This  theory,  strange  as  it  may  seem  to  us  now,  was 
founded  on  a  basis  of  actual  observation — not  entirely  on 
speculation.  Although  it  was  a  product  of  the  seventeenth 
century,  from  several  printed  accounts  one  is  likely  to  gather 
the  impression  that  it  arose  in  the  eighteenth  century,  and  that 


THE    RISE    OF    EMBRYOLOGY  207 

Bonnet,  Haller,  and  I^eibnitz  were  among  its  founders.  This 
implication  is  in  part  fostered  by  the  circumstance  that 
Swammerdam's  Bihlia  Naiurcg,  which  contains  the  germ  of 
the  theor}^,  was  not  pubHshed  until  1737 — more  than  half  a 
century  after  his  death — although  the  obser^^ations  for  it  were 
completed  before  Malpighi's  first  paper  on  embryology  was 
published  in  1672.  While  it  is  well  to  bear  in  mind  that  date 
of  publication,  rather  than  date  of  observation,  is  accepted 
as  establishing  the  period  of  emergence  of  ideas,  there  were 
other  men,  as  Malpighi  and  Leeuwenhoek,  contemporaries 
of  Swammerdam,  who  published  in  the  seventeenth  century 
the  basis  for  this  theory. 

Malpighi  supposed  (1672)  the  rudiment  of  the  embryo  to 
pre-exist  within  the  hen's  egg,  because  he  observed  evidences 
of  organization  in  the  unincubated  egg.  This  was  in  the 
heat  of  the  Italian  summer  (in  July  and  August,  as  he  him- 
self records),  and  Dareste  suggests  that  the  developmental 
changes  had  gone  forward  to  a  considerable  degree  before 
Malpighi  opened  the  eggs.  Be  this  as  it  may,  the  imperfec- 
tion of  his  instruments  and  technique  would  have  made  it 
very  difficult  to  see  anything  definitely  in  stages  under 
twenty-four  hours. 

In  reference  to  his  obser^^ations,  he  says  that  in  the  unin- 
cubated egg  he  saw  a  small  embryo  enclosed  in  a  sac  which 
he  subjected  to  the  rays  of  the  sun.  "Frequently  I  opened 
the  sac  with  the  point  of  a  needle,  so  that  the  animals  con- 
tained within  might  be  brought  to  the  light,  nevertheless  to 
no  purpose;  for  the  individuals  were  so  jelly-like  and  so  very 
small  that  they  were  lacerated  by  a  light  stroke.  Therefore, 
it  is  right  to  confess  that  the  beginnings  of  the  chick  pre-exist 
in  the  egg,  and  have  reached  a  higher  development  in  no  other 
way  than  in  the  eggs  of  plants."  ("  Quare  ptdli  stamina  in  ovo 
prcEexistere,  altioremque  originem  nacta  esse  fateri  convenit, 
haud  dispari  ritu,  ac  in  Plantarum  ovis.") 


2o8  BIOLOGY   AND    ITS    MAKERS 

Swammerdam  (1637-1680)  supplied  a  somewhat  better 
basis.  He  observed  that  the  parts  of  the  butterfly,  and  other 
insects  as  well,  are  discernible  in  the  chrysalis  stage.  Also, 
on  observing  caterpillars  just  before  going  into  the  pupa 
condition,  he  saw  in  outline  the  organs  of  the  future  stage, 
and  very  naturally  concluded  that  development  consists  of 
an  expansion  of  already  formed  parts. 

A  new  feature  was  introduced  through  the  discovery,  by 
Leeuwenhoek,  about  1677,*  of  the  fertilizing  filaments  of 
eggs.  Soon  after,  controversies  began  to  arise  as  to  whether 
the  embryo  pre-existed  in  the  sperm  or  in  the  egg.  By 
/  Leeuwenhoek,  Hartsoeker,  and  others  the  egg  was  looked 
upon  as  simply  a  nidus  within  which  the  sperm  developed, 
and  they  asserted  that  the  future  animal  existed  in  miniature 
in  the  sperm.  These  controversies  gave  rise  to  the  schools 
of  the  animalculists,  who  believed  the  sperm  to  be  the  animal 
germ.,  and  of  the  ovulists,  who  contended  for  the  ovum  in  that 
role. 

It  is  interesting  to  follow  the  metaphysical  speculations 
which  led  to  another  aspect  of  the  doctrine  of  pre-formation. 
There  were  those,  notably  Swammerdam,  Leibnitz,  and 
Bonnet,  who  did  not  hesitate  to  follow  the  idea  to  the  logical 
consequence  that,  if  the  animal  germ  exists  pre-formed,  one 
generation  after  another  must  be  encased  within  it.  This 
gave  rise  to  the  fanciful  idea  of  encasement  or  embottement, 
which  was  so  greatly  elaborated  by  Bonnet  and,  by  Leibnitz, 
applied  to  the  development  of  the  soul.  Even  Swammerdam 
(who,  by  the  way,  though  a  masterly  observer,  was  always 
a  poor  generalizer)  conceived  of  the  germs  of  all  forthcoming 
generations  as  having  been  located  in  the  common  mother 
Eve,  all  closely  encased  one  within  the  other,  like  the  boxes 
of  a  Japanese  juggler.     The  end  of  the  human  race  was  con- 

*  The  discovery  is  also  attributed  to  Harnm,  a  medical  student,  and  to 
Hartsoeker,  who  claimed  priority  in  the  discovery. 


/'"'^^ 


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-#-^34^:^^,, 


%f.^ 


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^Jonii^fjf, 


fm^ 


M 


Fig.   63. — Plate  from  Wollil'sTheoria  Generationis  (1759),  Showing 
Stages  in  the  Development  of  the  Chick. 


2IO  BIOLOGY   AND    ITS    MAKERS 

ceived  of  by  him  as  a  necessity,  when  the  last  germ  of  this 
wonderful  series  had  been  unfolded. 

His  successors,  in  efforts  to  compute  the  number  of 
homunculi  which  must  have  been  condensed  in  the  ovary  of 
Eve,  arrived  at  the  amazing  result  of  two  hundred  millions. 

Work  of  Wolff. — Friedrich  Kaspar  Wolff,  as  a  young 
man  of  twenty-six  years,  set  himself  against  this  grotesque 
doctrine  of  pre-formation  and  encasement  in  his  Theoria 
Generationis,  published  in  1759.  This  consists  of  three 
parts :  one  devoted  to  the  development  of  plants,  one  to  the 
development  of  animals,  and  one  to  theoretical  considera- 
tions. He  contended  that  the  organs  of  animals  make  their 
appearance  gradually,  and  that  he  could  actually  follow  their 
successive  stages  of  formation. 

The  figures  in  it  illustrating  the  development  of  the  chick, 
some  of  which  are  shown  in  Fig.  63,  are  not,  on  the  whole, 
so  good  as  Malpighi's.  Wolff  gives,  in  all,  seventeen  figures, 
while  Malpighi  published  eighty-six,  and  his  twenty  figures 
on  the  development  of  the  heart  are  more  detailed  than  any 
of  Wolff's.  When  the  figures  represent  similar  stages  of 
development,  a  comparison  of  the  two  men's  work  is  favor- 
able to  Malpighi.  The  latter  shows  much  better,  in  corre- 
sponding stages,  the  series  of  cerebral  vesicles  and  their  rela- 
tion to  the  optic  vesicles.  Moreover,  in  the  wider  range  of 
his  work,  he  shows  many  things — such  as  the  formation  of 
the  neural  groove,  etc. — not  included  in  Wolff's  observations. 
Wolff,  on  the  other  hand,  figures  for  the  first  time  the  prim- 
itive kidneys,  or  "Wolffian  bodies,"  of  which  he  was  the 
discoverer. 

Although  Wolff  was  able  to  show  that  development  con- 
sists of  a  gradual  formation  of  parts,  his  theory  of  develop- 
ment was  entirely  mystical  and  unsatisfactory.  The  fruitful 
idea  of  germinal  continuity  had  not  yet  emerged,  and  the 
thought  that   the  egg  has  inherited  an   organization   from 


THE    RISE    OF    EMBRYOLOGY  2II 

the  past  was  yet  to  be  expressed.  Wolff  was,  therefore,  in 
the  same  quandary  as  his  predecessors  when  he  undertook  to 
explain  development.  Since  he  assumed  a  total  lack  of 
organization  in  the  beginning,  he  was  obliged  to  make  devel- 
opment '^miraculous  "  through  the  action  on  the  egg  of  a 
hyperphysical  agent.  From  a  total  lack  of  organization,  he 
conceived  of  its  being  lifted  to  the  highly  organized  product 
through  the  action  of  a  "  vis  essentialis  corporis^ 

He  returned  to  the  problem  of  development  later,  and,  in 
1 768-1 769,  published  his  best  work  in  this  field  on  the  devel- 
opment of  the  intestine.*  This  is  a  very  original  and  strong 
piece  of  observational  work.  While  his  investigations  for  the 
Theoria  Generationis  did  not  reach  the  level  of  Malpighi's, 
those  of  the  paper  of  1 768  surpassed  them  and  held  the  posi- 
tion of  the  best  piece  of  embryological  work  up  to  that  of 
Pander  and  Von  Baer.  This  work  was  so  highly  appreciated 
by  Von  Baer  that  he  said:  ''It  is  the  greatest  masterpiece  of 
scientific  observation  v/hich  we  possess."  In  it  he  clearly 
demonstrated  that  the  development  of  the  intestine  and  its 
appendages  is  a  true  process  of  becoming.  Still  later,  in 
1789,  he  published  further  theoretical  considerations. 

Opposition  to  Wolff's  Views. — But  all  W^olff's  work  was 
launched  into  an  uncongenial  atmosphere.  The  great  physi- 
ologist Haller  could  not  accept  the  idea  of  epigenesis,  but 
opposed  it  energetically,  and  so  great  was  his  authority  that 
the  views  of  Wolff  gained  no  currenc}^.  This  retarded 
progress  in  the  science  of  anmial  development  for  more  than 
a  half -century. 

Bonnet  was  also  a  prolific  writer  in  opposition  to  the  ideas 
of  Wolff,  and  we  should  perhaps  have  a  portrait  of  him 
(Fig.  64)  as  one  of  the  philosophical  naturalists  of  the  time. 
His  prominent  connection  with  the  theory  of  pre-delineation 

*  De  Formatione  Intestinorum,  Nova  Commentar,  Ac.  Sci.  Petrop., 
St.  Petersburg,  XII.,  1768;  XIII.,  1769. 


212  BIOLOGY   AND    ITS    MAKERS 

in  its  less  grotesque  form,  his  discovery  of  the  development 
of  the  eggs  of  plant-lice  without  previous  fertilization,  his 
researches  on  regeneration  of  parts  in  polyps  and  worms, 
and  other  observations  place  him  among  the  conspicuous 


Fig.  64. — Charles  Bonnet,   1720-1793. 

naturalists  of  the  period.  His  system  of  philosophy,  which 
has  been  carefully  analyzed  by  Whitman,  is  designated  by 
that  writer  as  a  system  of  negations. 

In  1 82 1,  J.  Fr.  Meckel,  recognizing  the  great  value  of 


THE    RISE    OF    EMBRYOLOGY  213 

Wolff's  researches  on  the  development  of  the  intestines, 
rescued  the  work  from  neglect  and  obscurity  by  publishing 
a  German  translation  of  the  same,  and  bringing  it  to  the 
attention  of  scholars.  From  that  time  onward  Wolff's  labor 
was  fruitful. 

His  De  Formatione  Intestinorum  rather  than  his  Theoria 
Generationis  embodies  his  greatest  contribution  to  embry- 
ology. Not  only  is  it  a  more  fitting  model  of  observation,  but 
in  it  he  foreshadows  the  idea  of  germ-layers  in  the  embryo, 
which,  under  Pander  and  Von  Baer,  became  the  fundamental 
conception  in  structural  embryology.  Throughout  his  re- 
searches both  early  and  late,  he  likens  the  embryonic  rudiments, 
which  precede  the  formation  of  organs,  to  leaflets.  In  his 
work  of  1768  he  described  in  detail  how  the  leaf -like  layers 
give  rise  to  the  systems  of  organs ;  showing  that  the  nervous 
system  arises  first  from  a  leaf -like  layer,  and  is  followed, 
successively,  by  a  flesh  layer,  the  vascular  system,  and  lastly, 
by  the  intestinal  canal— all  arising  from  original  leaf-like 
layers. 

In  these  important  generalizations,  although  they  are 
verbally  incorrect,  he  reached  the  truth  as  nearly  as  it  was 
possible  at  the  time,  and  laid  the  foundation  of  the  germ- 
layer  theory. 

Wolff  was  a  man  of  great  power  as  an  obser/er,  and  al- 
though his  influence  was  for  a  long  time  retarded,  he  should 
be  recognized  as  the  foremost  investigator  in  embr}^olog}^ 
before  Von  Baer. 

Few  Biographical  Facts. — The  little  known  of  his  life 
is  gained  through  his  correspondence  and  a  letter  by  his 
amanuensis.  Through  personal  neglect,  and  hostility  to  his 
work,  he  could  not  secure  a  foothold  in  the  universities  of 
Germany,  and,  in  1764,  on  the  invitation  of  Catherine  of 
Russia,  he  went  to  the  Academy  of  Sciences  at  St.  Petersburg, 
where  he  spent  the  last  thirty  years  of  his  life. 


214  BIOLOGY   AND    ITS    MAKERS 

It  has  been  impossible  to  discover  a  portrait  of  Wolff, 
although  I  have  sought  one  in  various  ways  for  several  years. 
The  secretar}^  of  the  Academy  of  Sciences  at  St.  Petersburg 
writes  that  no  portrait  of  Wolff  exists  there,  and  that  the 
Academy  will  gratefully  receive  information  from  any  source 
regarding  the  existence  of  a  portrait  of  the  great  acade- 
mician. 

His  sincere  and  generous  spirit  is  shown  in  his  correspond- 
ence with  Haller,  his  great  opponent.  "  And  as  to  the  matter 
of  contention  between  us,  I  think  thus:  For  me,  no  more 
than  for  you,  glorious  man,  is  truth  of  the  very  greatest  con- 
cern. Whether  it  chance  that  organic  bodies  emerge  from 
an  invisible  into  a  visible  condition,  or  form  themselves  out 
of  the  air,  there  is  no  reason  why  I  should  wish  the  one  were 
truer  than  the  other,  or  wish  the  one  and  not  the  other.  And 
this  is  your  view  also,  glorious  man.  We  are  investigating 
for  truth  only ;  we  seek  that  which  is  true.  Why  then  should 
I  contend  with  you?"     (Quoted  from  Wheeler.) 

The  Period  of  Von  Baer 

What  Johannes  MuUer  was  for  physiology,  von  Baer 
was  for  embryology;  all  subsequent  growth  was  influenced 
by  his  investigations. 

The  greatest  classic  in  embryology  is  his  Development  of 
Animals  (Entwickelungsgeschichte  der  Tiere — Beohachtung 
nnd  Reflexion),  the  first  part  of  which  was  published  in  1828, 
and  the  work  on  the  second  part  completed  in  1834,  although 
it  was  not  published  till  1837.  This  second  part  was  never 
finished  according  to  the  plan  of  Von  Baer,  but  was  issued  by 
his  publisher,  after  vainly  waiting  for  the  finished  manu- 
script. The  final  portion,  which  Von  Baer  had  withheld,  in 
order  to  perfect  in  some  particulars,  was  published  in  1888, 
after  his  death,  but  in  the  form  in  which  he  left  it  in  1834. 


THE    RISE    OF    EMBRYOLOGY  215 

The  observations  for  the  first  part  began  in  1819,  after  he 
had  received  a  copy  of  Pander's  researches,  and  covered  a 
period  of  seven  years  of  close  devotion  to  the  subject;  and 
the  observations  for  the  last  part  were  carried  on  at  interv^als 
for  several  years. 

It  is  significant  of  the  character  of  his  Reflexionen  that, 
although  published  before  the  announcement  of  the  cell- 
theor}^,  and  before  the  acceptance  of  the  doctrine  of  organic 
evolution,  they  have  exerted  a  molding  influence  upon 
embryology  to  the  present  time.  The  position  of  von  Baer 
in  embryology  is  owing  as  much  to  his  sagacity  in  specula- 
tion as  to  his  powers  as  an  observer.  "Never  again  have 
observation  and  thought  been  so  successfully  combined  in 
embryological  work  "  (Minot). 

Von  Baer  was  bom  in  1792,  and  lived  on  to  1876,  but  his 
enduring  fame  in  embryology  rests  on  work  completed  more 
than  forty  years  before  the  end  of  his  useful  life.  After  his 
removal  from  Konigsberg  to  St.  Petersburg,  in  1834,  he  very 
largely  devoted  himself  to  anthropology  in  its  widest  sense, 
and  thereby  extended  his  scientific  reputation  into  other 
fields. 

If  space  permitted,  it  would  be  interesting  to  give  the 
biography*  of  this  extraordinary  man,  but  here  it  will  be 
necessary  to  content  ourselves  with  an  examination  of  his 
portraits  and  a  brief  account  of  his  work. 

Portraits. — Several  portraits  of  von  Baer  showing  him 
at  different  periods  of  his  life  have  been  published.  A  very 
attractive  one,  taken  in  his  early  manhood,  appeared  in 
Harper^ s  Magazine  for  1898.  The  expression  of  the  face  is 
poetical,  and  the  picture  is  interesting  to  compare  with  the 
more  matured,  sage-like  countenance  forming  the  frontispiece 

*  Besides  biographical  sketches  by  Stieda,  Waldeyer,  and  others,  we  have 
a  very  entertaining  autobiography  of  Von  Baer,  published  in  1864,  for  pri- 
vate circulation,  but  afterward  (1866)  reprinted  and  placed  on  sale. 


2l0 


BIOLOGY   AND    ITS    MAKERS 


of  Stieda's  Life  of  Von  Baer  (see  Fig.  65).  This,  perhaps 
the  best  of  all  his  portraits,  shows  him  in  the  full  devel- 
opment of  his  powers.     An  examination  of  it  impresses  one 


Fig.  65. — Karl  Ernst  von  Baer,  1792-1876. 

with  confidence  in  his  balanced  judgment  and  the  thorough- 
ness and  profundity  of  his  mental  operations. 

The  portrait  of  Von  Baer  at  about  seventy  years  of  age, 


THE  RISE   OF   EMBRYOLOGY  217 

reproduced  in  Fig.  66,  is,  however,  destined  to  be  the  one  by 
which  he  is  commonly  known  to  embryologists,  since  it  forms 
the  frontispiece  of  the  great  cooperative  Handbook  oj  Em- 


FiG.  66. — ^VoN  Baer  at  about  Seventy  Years  of  Age. 

bryology  just   pubhshed    under    the  editorship    of   Oskar 
Hertwig. 

Von  Baer's  Especial  Service. — Apart  from   special  dis- 


2l8  BIOLOGY   AND    ITS    MAKERS 

coveries,  Von  Baer  greatly  enriched  embr}^ology  in  three  di- 
rections :  In  the  first  place,  he  set  a  higher  standard  for  all 
work  in  embryology,  and  thereby  lifted  the  entire  science  to 
a  higher  level.  Activity  in  a  great  field  of  this  kind  is,  with 
the  rank  and  file  of  workers,  so  largely  imitative  that  this 
feature  of  his  influence  should  not  be  overlooked.  In  the 
second  place,  he  established  the  germ-layer  theory,  and,  in 
the  third,  he  made  embryology  comparative. 

In  reference  to  the  germ-layer  theory,  it  should  be  recalled 
that  Wolff  had  distinctly  foreshadowed  the  idea  by  showing 
that  the  material  out  of  which  the  embryo  is  constructed  is, 
in  an  early  stage  of  development,  arranged  in  the  form  of 
leaf-like  layers.  He  showed  specifically  that  the  alimentary 
canal  is  produced  by  one  of  these  sheet-like  expansions  fold- 
ing and  rolling  together. 

Pander,  by  observations  on  the  chick  (1817),  had  ex- 
tended the  knowledge  of  these  layers  and  elaborated  the 
conception  of  Wolff.  He  recognized  the  presence  of  three 
primary  layers — an  outer,  a  middle,  and  an  inner — out  of 
which  the  tissues  of  the  body  are  formed. 

The  Germ-Layers.— But  it  remained  for  Von  Baer,*  by 
extending  his  observ^ations  into  all  the  principal  groups  of 
animals,  to  raise  this  conception  to  the  rank  of  a  general  lav/ 
of  development.     He  was  able  to  show  that  in  all  animals 

*  It  is  of  more  than  passing  interest  to  remember  that  Pander  and  Von 
Baer  were  associated  as  friends  and  fellow -students,  under  Dollinger  at 
Wiirzburg.  It  was  partly  through  the  influence  of  Von  Baer  that  Pander 
came  to  study  with  DoUinger,  and  took  up  investigations  on  development. 
His  ample  private  means  made  it  possible  for  him  to  bear  the  expenses  con- 
nected with  the  investigation,  and  to  secure  the  services  of  a  fine  artist  for 
making  the  illustrations.  The  result  was  a  magnificently  illustrated  treatise. 
His  unillustrated  thesis  in  Latin  (1817)  is  more  commonly  known,  but  the 
illustrated  treatise  in  German  is  rarer.  Von  Baer  did  not  take  up  his  re- 
searches seriously  until  Pander's  were  published.  It  is  significant  of  their 
continued  harmonious  relations  that  Von  Baer's  work  is  dedicated  "  An 
meinen  Jugendfreund,  Dr.  Christian  Pander." 


I 


THE    RISE    OF    EMBRYOLOGY  219 

except  the  very  lowest  there  arise  in  the  course  of  devel- 
opment leaf-like  layers,  which  become  converted  into  the 
"fundamental  organs"  of  the  body. 

Now,  these  elementary  layers  are  not  definitive  tissues  of 
the  body,  but  are  embryonic,  and  therefore  may  appropriately 
be  designated  "germ-layers."  The  conception  that  these 
germ-layers  are  essentially  similar  in  origin  and  fate  in  all 
animals  was  a  fuller  and  later  development  of  the  germ-layer 
theory,  a  conception  which  dominated  embryological  study 
until  a  recent  date. 

Von  Baer  recognized  four  such  layers;  the  outer  and  inner 
ones  being  formed  first,  and  subsequently  budding  off  a 
middle  layer  composed  of  two  sheets.  A  little  later  (1845) 
Remak  recognized  the  double  middle  layer  of  Von  Baer  as  a 
unit,  and  thus  arrived  at  the  fundamental  conception  of  three 
layers — the  ecto-,  endo-,  and  mesoderm — which  has  so  long 
held  sway.  For  a  long  time  after  Von  Baer  the  aim  of  em- 
bryologists  was  to  trace  the  history  of  these  germ-layers,  and 
so  in  a  wider  and  miuch  qualified  sense  it  is  to-day. 

It  will  ever  stand  to  his  credit,  as  a  great  achievement, 
that  Von  Baer  was  able  to  make  a  very  complicated  feature 
of  development  clear  and  relatively  simple.  Given  a  leaf -like 
rudiment,  with  the  layers  held  out  by  the  yolk,  as  is  the  case 
in  the  hen's  egg,  it  was  no  easy  matter  to  conceive  how 
they  are  transformed  into  the  nerv^ous  system,  the  body-wall, 
the  alimentary  canal,  and  other  parts,  but  Von  Baer  saw 
deeply  and  clearly  that  the  fundamental  anatomical  features 
of  the  body  are  assumed  by  the  leaf -like  rudiments  being 
rolled  into  tubes. 

Fig.  67  shows  four  sketches  taken  from  the  plates  illus- 
trating von  Baer's  work.  At  A  is  shown  a  stage  in  the  forma- 
tion of  the  embryonic  envelope,  or  amnion,  which  surrounds 
the  embryos  of  all  animals  above  the  cla:ss  of  amphibia.  Bj 
another  figure  of  an  ideal  section,  shows  that,  long  before  the 


220  BIOLOGY   AND    ITS    MAKERS 

day  of  microtomes,  Von  Baer  made  use  of  sections  to  represent 
the  relationships  of  his  four  germ-layers.  At  C  and  D  is 
represented  diagrammatically  the  way  in  which  these  layers 
are  rolled  into  tubes.  He  showed  that  the  central  nervous 
system  arose  in  the  form  of  a  tube,  from  the  outer  layer ;  the 
body -wall  in  the  form  of  a  tube,  composed  of  skin  and  muscle 
layers;  and  the  alimentary  tube  from  mucous  and  vascular 
layers. 

The  generalization  that  embryos  in  development  tend  to 
recapitulate  their  ancestral  history  is  frequently  attributed  to 
Von  Baer,  but  the  qualified  way  in  which  he  suggests  some- 
thing of  the  sort  will  not  justify  one  in  attaching  this  con- 
clusion to  his  work. 

Von  Baer  was  the  first  to  make  embryology  truly  com- 
parative, and  to  point  out  its  great  value  in  anatomy  and 
zoology.  By  embryological  studies  he  recognized  four  types 
of  organization — as  Cuvier  had  done  from  the  standpoint  of 
comparative  anatomy.  But,  since  these  types  of  organiza- 
tion have  been  greatly  changed  and  subdivided,  the  impor- 
tance of  the  distinction  has  faded  away.  As  a  distinct  break, 
however,  with  the  old  idea  of  a  linear  scale  of  being  it  was 
of  moment. 

Among  his  especially  noteworthy  discoveries  may  be 
mentioned  that  of  the  egg  of  mammals  (1827),  and  the  noto- 
chord  as  occurring  in  all  vertebrate  animals.  His  discovery 
of  the  mammalian  egg  had  been  preceded  by  Purkinje's 
observations  upon  the  germinative  spot  in  the  bird's  egg 

(1825). 

Von  Baer*s  Rank. — Von  Baer  has  come  to  be  dignified 
with  the  title  of  the  "father  of  modern  embryology."  No 
man  could  have  done  more  in  his  period,  and  it  is  owing  to 
his  superb  intellect,  and  to  his  talents  as  an  observer,  that  he 
accomplished  what  he  did.  As  Minot  says:  "He  worked 
out,  almost  as  fully  as  was  possible  at  this  time,  the  genesis 


Fig.  67. — Sketches  from  Von  Baer's  Embryological  Treatise  (1828). 


222  BIOLOGY   AND    ITS    MAKERS 

of  all  the  principal  organs  from  the  germ-layers,  instinctively 
getting  at  the  truth  as  only  a  great  genius  could  have  done." 

After  his  masterly  work,  the  science  of  embryology  could 
never  return  to  its  former  level;  he  had  given  it  a  new  direc- 
tion, and  through  his  influence  a  period  of  great  activity  was 
introduced. 

The  Period  from  Von  Baer  to  Balfour 

In  the  period  between  Von  Baer  and  Balfour  there  were 
great  general  advances  in  the  knowledge  of  organic  structure 
that  brought  the  whole  process  of  development  into  a  new 
light. 

Among  the  most  important  advances  are  to  be  enumerated 
the  announcement  of  the  cell-theory,  the  discovery  of  proto- 
plasm, the  beginning  of  the  recognition  of  germinal  continuity, 
and  the  establishment  of  the  doctrine  of  organic  evolution. 

The  Cell-Theory. — ^The  generalization  that  the  tissues  of 
all  animals  and  plants  are  structurally  composed  of  similar 
units,  called  cells,  was  given  to  the  world  through  the  com- 
bined labors  of  Schleiden  and  Schwann.  The  history  of  this 
doctrine,  together  with  an  account  of  its  being  remodeled 
into  the  protoplasm  doctrine,  is  given  in  Chapter  XII. 

The  broad -reaching  effects  of  the  cell-theory  may  be  easily 
imagined,  since  it  united  all  animals  on  the  broad  plane  of 
likeness  in  microscopic  structure.  Now  for  the  first  time 
the  tissues  of  the  body  were  analyzed  into  their  units ;  now 
for  the  first  time  was  comprehended  the  nature  of  the  germ- 
layers  of  Von  Baer. 

Among  the  first  questions  to  emerge  in  the  light  of  the  new 
researches  were  concerning  the  origin  of  cells  in  the  organs, 
the  tissues,  and  the  germ-layers.  The  road  to  the  investiga- 
tion of  these  questions  was  already  opened,  and  it  was  fol- 
lowed, step  by  step,  until  the  egg  and  the  sperm  came  to  be 


THE    RISE    OF    EMBRYOLOGY  223 

recognized  as  modified  cells.  This  position  was  reached, 
for  the  egg,  about  1861,  when  Gegenbaur  showed  that  the 
eggs  of  all  vertebrate  animals,  regardless  of  size  and  con- 
dition, are  in  reality  single  cells.  The  sperm  was  put  in  the 
same  category  about  1865. 

The  rest  was  relatively  easy:  the  egg,  a  single  cell,  by 
successive  divisions  produces  many  cells,  and  the  arrange- 
ment of  these  into  primary  embryonic  layers  brings  us  to  the 
starting-point  of  Wolff  and  Von  Baer.  The  cells,  continuing 
to  multiply  by  division,  not  only  increase  in  number,  but  also 
undergo  changes  through  division  of  physiological  labor, 
whereby  certain  groups  are  set  apart  to  perform  a  particular 
part  of  the  work  of  the  body.  In  this  way  arise  the  various 
tissues  of  the  body,  which  are,  in  reality,  similar  cells  per- 
forming a  similar  function.  Finally,  from  combinations  of 
tissues,  the  organs  are  formed. 

But  the  egg,  before  entering  on  the  process  of  develop- 
ment, must  be  stimulated  by  the  union  of  the  sperm  with  the 
nucleus  of  the  egg,  and  thus  the  starting-point  of  every  animal 
and  plant,  above  the  lowest  group,  proves  to  be  a  single  cell 
with  protoplasm  derived  from  two  parents.  While  questipns 
regarding  the  origin  of  cells  in  the  body  were  being  answered, 
the  foundation  for  the  embr}^ological  study  of  heredity  was 
also  laid. 

Advances  were  now  more  rapid  and  more  sure;  flashes  of 
morphological  insight  began  to  illuminate  the  way,  and  the 
facts  of  isolated  observations  began  to  fit  into  a  harmonized 
whole. 

Apart  from  the  general  advances  of  this  period,  men- 
tioned in  other  connections,  the  work  of  a  few  individuals 
requires  notice. 

Rathke  and  Remak  wxre  engaged  with  the  broader  aspects 
of  embryology,  as  well  as  with  special  investigations.  From 
Rathke's  researches  came  great  advances  in  the  knowledge  of 


224  BIOLOGY   AND    ITS    MAKERS 

the  development  of  insects  and  other  invertebrates,  and  Remak 
is  notable  for  similar  work  with  the  vertebrates.  As  already 
mentioned,  he  was  the  first  to  recognize  the  middle  layer  as 
a  unit,  through  which  the  three  germ-layers  of  later  embry- 
ologists  emerged  into  the  literature  of  the  subject. 

Koelliker,  i8i 7-1905,  the  veteran  embryologist,  for  so 
many  years  a  professor  in  the  University  of  Wiirzburg,  carried 
on  investigations  on  the  segmentation  of  the  egg.  Besides 
work  on  the  invertebrates,  later  he  followed  with  care  the 
development  of  the  chick  and  the  rabbit;  he  encompassed 
the  whole  field  of  embryology,  and  published,  in  1861  and 
again  in  1876,  a  general  treatise  on  vertebrate  embryology, 
of  high  merit.  The  portrait  of  this  distinguished  man  is 
shown  in  Chapter  VIII,  where  also  his  services  as  a  histologist 
are  recorded. 

Huxley  took  a  great  step  toward  unifying  the  idea  of  germ- 
layers  throughout  the  animal  kingdom,  when  he  maintained, 
in  1849,  that  the  two  cell-layers  in  animals  like  the  hydra 
and  oceanic  hydrozoa  correspond  to  the  ectoderm  and 
endoderm  of  higher  animals. 

Kow^alevsky  (Fig.  68)  made  interesting  discoveries  of  a 
general  bearing.  In  1866  he  showed  the  practical  identity, 
in  the  early  stages  of  development,  between  one  of  the  lowest 
vertebrates  (amphioxus)  and  a  tunicate.  The  latter  up  to 
that  time  had  been  considered  an  invertebrate,  and  the  effect 
of  Kowalevsky's  observations  was  to  break  down  the  sharply 
limited  line  supposed  to  exist  between  the  invertebrates  and 
the  vertebrates.  This  was  of  great  influence  in  subsequent 
work.  Kowalevsky  also  founded  the  generalization  that  all 
animals  in  development  pass  through  a  gastrula  stage — a 
doctrine  associated,  since  1874,  with  the  name  of  Haeckel 
under  the  title  of  the  gastraea  theory. 

Beginning  of  the  Doctrine  of  Germinal  Continuity. — 
The  conception  that  there  is  unbroken  continuity  of  germinal 


THE    RISE    OF    EMBRYOLOGY  225 

substance  between  all  living  organisms,  and  that  the  egg  and 
the  sperm  are  endowed  with  an  inherited  organization  of 
great  complexity,  has  become  the  basis  for  all  current  theories 
of  heredity  and  development.  So  much  is  involved  in  this 
conception  that,  in  the  present  decade,  it  has  been  designated 
(Whitman)  "  the  central  fact  of  modem  biology."  The  first 
clear  expression  of  it  is  found  in  Virchow's  Cellular  Pa- 
thology, published  in  1858.     It  was  not,  however,  until  the 


Fig.  68. — A.  Kowalevsky,   1840-1901. 

period  of  Balfour,  and  through  the  work  of  Fol,  Van  Beneden 
(chromosomes,  1883),  Boveri,  Hertwig,  and  others,  that  the 
great  importance  of  this  conception  began  to  be  appreciated, 
and  came  to  be  woven  into  the  fundamental  ideas  of  de- 
velopment. 

Influence  of  the  Doctrine  of  Organic  Evolution. — ^This 

doctrine,  although  founded  in  its  modern  sense  by  Lamarck 

in  the  early  part  of  the  nineteenth  century,  lay  dormant  until 

Darwin,  in  1859,  brought  a  new  feature  into  its  discussion 

15 


226  BIOLOGY    AND    ITS    MAKERS 

by  emphasizing  the  factor  of  natural  selection.  The  general 
acceptance  of  the  doctrine,  which  followed  after  fierce  oppo- 
sition, had,  of  course,  a  profound  influence  on  embryology. 
The  latter  science  is  so  intimately  concerned  with  the  gene- 
alogy of  animals  and  plants,  that  the  newly  accepted  doc- 
trine, as  affording  an  explanation  of  this  genealogy,  was  the 
thing  most  needed. 

The  development  of  organisms  was  now  seen  in  the  light 
of  ancestral  history,  rudim_entary  organs  began  to  have 
meaning  as  hereditary  survivals,  and  the  whole  process  of 
development  assumed  a  dift'erent  aspect.  This  doctrine 
supplied  a  new  impulse  to  the  interpretation  of  nature  at 
large,  and  of  the  embr^^ological  record  in  particular.  The 
meaning  of  the  embryological  record  was  so  greatly  em- 
phasized in  the  period  of  Balfour  that  it  will  be  commented 
upon  under  the  next  division  of  our  subject. 

The  period  between  Von  Baer  and  Balfour  proved  to  be 
one  of  great  importance  on  account  of  the  general  advances 
in  knowledge  of  all  organic  nature.  Observ^ations  were 
moving  toward  a  better  and  more  consistent  conception  of 
the  structure  of  animals  and  plants.  A  new  comparative 
anatomy,  more  profound  and  richer  in  meaning  than  Cu- 
vier's,  was  arising.  The  edifice  on  the  foundation  of  Von 
Baer's  work  was  now  emerging  into  recognizable  outlines. 

The  Period  of  Balfour,  with  an  Indication  of  Present 
Tendencies 

Balfour's  Masterly  Work.— The  workers  of  this  period 
inherited  all  the  accumulations  of  previous  efforts,  and  the 
time  was  ripe  for  a  new  step.  Observations  on  the  develop- 
ment of  different  animals,  vertebrates  and  invertebrates,  had 
accumulated  in  great  number,  but  they  w^ere  scattered 
through  technical  periodicals,  transactions  of  learned  societies, 


THE    RISE    OF    EMBRYOLOGY 


227 


monographs,  etc.,  and  there  was  no  compact  science  of  em- 
bryology with  definite  outlines.  Balfour  reviewed  all  this 
mass  of  information,  digested  it,  and  molded  it  into  an  organ- 
ized wliole.  The  results  were  published  in  the  form  of  two 
volumes  with  the  title  of  Comparative  Embryology.  This 
book  of  "almost  priceless  value"  was  given  to  the  world  in 
1880-1881.     It  was  a  colossal  undertaking,  but  Balfour  was 


Fig.  69. — Francis  M.  Balfour,   1851-1882. 


a  phenomenal  worker.  Before  his  untimely  death  at  the  age 
of  thirty-one,  he  had  been  able  to  complete  this  work  and  to 
produce,  besides,  a  large  number  of  technical  researches. 
The  period  of  Balfour  is  taken  arbitrarily  in  this  volume  as 
beginning  about  1874,  when  he  published,  with  Michael 
Foster,  The  Elements  of  Embryology. 

His  University  Career. — Balfour  (Fig.  69)  was  bom  in 


228  BIOLOGY   AND    ITS    MAKERS 

1 85 1.  During  his  days  of  preparation  for  the  university  he 
was  a  good  student,  but  did  not  exhibit  in  any  marked  way 
the  powers  for  which  later  he  became  distinguished.  At 
Cambridge,  his  distinguished  teacher,  the  late  Sir  Michael 
Foster,  recognized  his  great  talents,  and  encouraged  him  to 
begin  work  in  embryology.  His  labors  in  this  field  once 
begun,  he  threw  himself  into  it  with  great  intensity.  He  rose 
rapidly  to  a  professorship  in  Cambridge,  and  so  great  was 
his  enthusiasm  and  earnestness  as  a  lecturer  that  in  seven 
years  "  voluntaiy  attendance  on  his  classes  advanced  from 
ten  to  ninety."  He  was  also  a  stimulator  of  research,  and  at 
the  time  of  his  death  there  were  twenty  students  engaged  in 
his  laboratory  on  problems  of  development. 

He  was  distinguished  for  personal  attractiveness,  and 
those  who  met  him  were  impressed  with  his  great  sincerity, 
as  well  as  his  personal  charm.  He  was  welcomed  as  an 
addition  to  the  select  group  of  distinguished  scientific  men  of 
England,  and  a  great  career  was  predicted  for  him.  Huxley, 
when  he  felt  the  call,  at  a  great  personal  sacrifice,  to  lay  aside 
the  more  rigorous  pursuits  of  scientific  research,  and  to  devote 
himself  to  molding  science  into  the  lives  of  the  people,  said 
of  Balfour:  "He  is  the  only  man  who  can  carry  out  my 
work." 

His  Tragic  Fate. — But  that  was  not  destined  to  be.  The 
story  of  his  tragic  end  need  be  only  referred  to.  After  com- 
pleting the  prodigious  labor  on  the  Comparative  Embry- 
ology he  went  to  Switzerland  for  recuperation,  and  met  his 
death,  with  that  of  his  guide,  by  slipping  from  an  Alpine 
height  into  a  chasm.     His  death  occurred  in  July,  1882. 

The  memorial  edition  of  his  works  fills  four  quarto  vol- 
umes, but  the  ''Comparative  Embryology"  is  Balfour's 
monument,  and  will  give  him  enduring  fame.  It  is  not  only 
a  digest  of  the  work  of  others,  but  contains  also  general 
considerations   of  a   far-seeing   quality.     He  saw  develop- 


THE    RISE    OF    EMBRYOLOGY  229 

mental  processes  in  the  light  of  the  hypothesis  of  organic 
evolution.  His  speculations  were  sufficiently  reserved,  and 
nearly  always  luminous.  It  is  significant  of  the  character 
of  this  work  to  say  that  the  speculations  contained  in  the 
papers  of  the  rank  and  file  of  embryological  workers  for  more 
than  two  decades,  and  often  fondly  believed  to  be  novel, 
were  for  the  most  part  anticipated  by  Balfour,  and  were  also 
better  expressed,  with  better  qualifications. 

The  reading  of  ancestral  history  in  the  stages  of  develop- 
ment is  such  a  characteristic  feature  of  the  embryological 
work  of  Balfour's  period  that  some  observ^ations  concerning 
it  will  now  be  in  place. 

Interpretation  of  the  Embryological  Record. — Perhaps 
the  most  impressive  feature  of  animal  development  is  the 
series  of  similar  changes  through  which  all  pass  in  the  embr}^o. 
The  higher  animals,  especially,  exhibit  all  stages  of  organiza- 
tion from  the  unicellular  fertilized  ovum  to  the  fully  formed 
animal  so  far  removed  from  it.  The  intermediate  changes 
constitute  a  long  record,  the  possibility  of  interpreting  which 
has  been  a  stimulus  to  its  careful  examination. 

Meckel,  in  182 1,  and  later  Von  Baer,  indicated  the  close 
similarity  between  embryonic  stages  of  widely  different 
animals;  Von  Baer,  indeed,  confessed  that  he  was  unable  to 
distinguish  positively  between  a  reptile,  a  bird,  and  a  mam- 
malian embryo  in  certain  early  stages  of  growth. 

In  addition  to  this  similarity,  which  is  a  constant  feature  of 
the  embryological  record,  there  is  another  one  that  may  be 
equally  significant ;  viz.,  in  the  course  of  embryonic  history, 
sets  of  rudimentary  organs  arise  and  disappear.  Rudiment- 
ary teeth  make  their  appearance  in  the  embr}^'o  of  the  wdiale- 
bone  whale,  but  they  are  transitory  and  soon  disappear  with- 
out having  been  of  service  to  the  animal.  In  the  embrj'os 
of  all  higher  vertebrates,  as  is  well  know^n,  gill-clefts  and 
gill-arches  with  an  appropriate  circulation,  make  their  ap- 


230  BIOLOGY   AND    ITS    MAKERS 

pcarancc,  but  disappear  long  before  birth.  These  indica- 
tions, and  similar  ones,  must  have  some  meaning. 

Now  whatever  qualities  an  animal  exhibits  after  birth 
are  attributed  to  heredity.  May  it  not  be  that  all  the  inter- 
mediate stages  are  also  inheritances,  and,  therefore,  represent 
phases  in  ancestral  history?  If  they  be,  indeed,  clues  to 
ancestral  conditions,  m.ay  we  not,  by  patching  together  our 
observations,  be  able  to  interpret  the  record,  just  as  the  his- 
tory of  ancient  peoples  has  been  made  out  from  fragments 
in  the  shape  of  coins,  vases,  implements,  hieroglyphics,  in- 
scriptions, etc.? 

The  Recapitulation  Theory. — The  results  of  reflection  in 
this  direction  led  to  the  foundation  of  the  recapitulation 
theory,  according  to  which  animals  are  supposed,  in  their 
individual  development,  to  recapitulate  to  a  considerable 
degree  phases  of  their  ancestral  history.  This  is  one  of  the 
widest  generalizations  of  embryology.  It  was  suggested  in 
the  writings  of  Von  Baer  and  Louis  Agassiz,  but  received  its 
first  clear  and  complete  expression  in  1863,  in  the  writings  of 
Fritz  Muller. 

Although  the  course  of  events  in  development  is  a  record, 
it  is,  at  best,  only  a  fragmentary  and  imperfect  one.  Many 
stages  have  been  dropped  out,  others  are  unduly  prolonged 
or  abbreviated,  or  appear  out  of  chronological  order,  and, 
besides  this,  some  of  the  structures  have  arisen  from  adapta- 
tion of  a  particular  organism  to  its  conditions  of  develop- 
ment, and  are,  therefore,  not  ancestral  at  all,  but,  as  it  were, 
recent  additions  to  the  text.  The  interpretation  becomes  a 
difficult  task,  which  requires  much  balance  of  judgment  and 
profound  analysis. 

The  recapitulation  theory  was  a  dominant  note  in  all 
Balfour's  speculations,  and  in  that  of  his  contemporary  and 
fellow-student  Marshall.  It  has  received  its  most  sweeping 
application  in  the  works  of  Ernst  Haeckel. 


THE    RISE    OF    EMBRYOLOGY  23I 

Widely  spread  throughout  recent  literature  is  to  be  noted 
a  reaction  against  the  too  wide  and  unreserved  application 
of  this  doctrine.  This  is  naturally  to  be  expected,  since  it 
is  the  common  tendency  in  all  fields  of  scholarship  to  demand 


Fig.   70. — OsKAR  Hertwig  in   1890. 

a  more  critical  estimate  of  results,  and  to  undergo  a  reaction 
from  the  earlier  crude  and  sweeping  conclusions. 

Nearly  all  problems  in  anatomy  and  structural  zoology 
are  approached  from  the  embryological  side,  and,  as  a  con- 
sequence, the  work  of  the  great  army  of  anatomists  and 


232  BIOLOGY    AND    ITS    MAKERS 

zoologists  has  been  in  a  measure  embryological.  Many  of 
them  have  produced  beautiful  and  important  researches,  but 
the  work  is  too  extended  to  admit  of  review  in  this  connection. 

Oskar  Hertwig,  of  Berlin  (Fig.  70),  is  one  of  the  repre- 
sentative embryologists.  of  Europe,  while,  in  this  country, 
lights  of  the  first  magnitude  are  Brooks,  Minot,  Whitman, 
E.  B.  Wilson,  and  others. 

Although  no  attempt  is  made  to  review  the  researches  of 
the  xCcent  period,  we  cannot  pass  entirely  without  mention 
the  discovery  of  chromosomes,  and  of  their  reduction  in  the 
ripening  of  the  egg  and  in  the  formation  of  sperm.  This  has 
thrown  a  flood  of  light  on  the  phenomena  of  fertilization,  and 
has  led  to  the  recognition  of  chromosomes  as  probably  the 
bearers  of  heredity.  The  nature  of  fertilization,  investigated 
by  Fol,  O.  Hertwig,  and  others,  formed  the  starting-point  for 
a  series  of  brilliant  discoveries. 

The  embryological  investigations  of  the  late  Wilhelm  His 
(Fig.  71)  are  also  deserving  of  especial  notice.  His  luminous 
researches  on  the  development  of  the  ners^ous  system,  the 
origin  of  nerve  fibers,  and  his  analysis  of  the  development  of 
the  human  embryo  are  all  veiy  important. 

Recent  Tendencies.  Experimental  Embryology. — Soon 
after  the  publication  of  Balfour's  great  work  on  "  Comparative 
Embryology,"  a  new  tendency  in  research  began  to  appear 
which  led  onward  to  the  establishment  of  experimental  em- 
brj'ology.  All  previous  work  in  this  field  had  been  concerned 
with  the  structure,  or  architecture,  of  organisms,  but  now  the 
physiological  side  began  to  receive  attention.  Whitman  has 
stated  with  great  aptness  the  interdependence  of  these  two 
lines  of  work,  as  follows:  " Morphology  raises  the  question^ 
How  came  the  organic  mechanism  into  existence?  Has  it 
had  a  history,  reaching  its  present  stage  of  perfection  through 
a  long  series  of  gradations,  the  first  term  of  which  w^as  a 
relatively  simple  stage  ?    The  embryological  history  is  traced 


Fig.  71. — WiLHELM  His,  1831-1904.     At  Sixty-four  Years. 


234  BIOLOGY   AND    ITS    MAKERS 

out,  and  the  palaeontological  records  are  searched,  until  the 
evidence  from  both  sources  establishes  the  fact  that  the  organ 
or  organism  under  study  is  but  the  summation  of  modifica- 
tions and  elaborations  of  a  relatively  simple  primordial.  This 
point  settled,  physiology  is  called  upon  to  complete  the  story. 
Have  the  functions  remained  the  same  through  the  series? 
or  have  they  undergone  a  series  of  modifications,  differentia- 
tions, and  improvements  more  or  less  parallel  with  the  mor- 
phological series?" 

Since  physiolog}^  is  an  experimental  science,  all  questions 
of  this  nature  must  be  investigated  with  the  help  of  experi- 
ments. Organisms  undergoing  development  have  been  sub- 
jected to  changed  conditions,  and  their  responses  to  various 
forms  of  stimuli  have  been  noted.  In  the  rise  of  experimental 
embryology  we  have  one  of  the  most  promising  of  the  recent 
departures  from  the  older  aspects  of  the  subject.  The  results 
already  attained  in  this  attractive  and  suggestive  field  make 
too  long  a  story  to  justify  its  telling  in  this  volume.  Roux, 
Herbst,  Loeb,  Morgan,  E.  B.  Wilson,  and  many  others  have 
contributed  to  the  grov/th  of  this  new  division  of  embryology. 
Good  reasons  have  been  adduced  for  believing  that  qualitative 
changes  take  place  in  the  protoplasm  as  development  pro- 
ceeds. And  a  curb  has  been  put  upon  that  ''great  fault  of 
embryology,  the  tendency  to  explain  any  and  every  operation 
of  development  as  merely  the  result  of  inheritance."  It  has 
been  demonstrated  that  surrounding  conditions  have  much 
to  do  with  individual  development,  and  that  the  course  of 
events  may  depend  largely  upon  stimuli  coming  from  with- 
out, and  not  exclusively  on  an  inherited  tendency. 

Cell-Lineage. — Investigations  on  the  structural  side  have 
reached  a  high  grade  of  perfection  in  studies  on  cell-lineage. 
The  theoretical  conclusions  in  the  germ-layer  theory  are 
based  upon  the  assumption  of  identity  in  origin  of  the  differ- 
ent layers.    But  the  lack  of  agreement  among  observ^ers,  espe- 


THE    RISE    OF    EMBRYOLOGY  235 

cially  in  reference  to  the  origin  of  the  mesoderm,  made  it 
necessary  to  study  more  closely  the  early  developmental  stages 
before  the  establishment  of  the  germ-layers.  It  is  a  great 
triumph  of  exact  observation  that,  although  continually 
changing,  the  consecutive  history  of  the  individual  cells  has 
been  followed  from  the  beginning  of  segmentation  to  the  time 
v^^hen  the  germ-layers  are  established.  Some  of  the  beautifully 
illustrated  memoirs  in  this  field  are  highly  artistic. 

Blochman  (1882)  was  a  pioneer  in  observations  of  this 
kind,  and,  following  him,  a  number  of  American  investigators 
have  pursued  studies  on  cell-lineage  with  great  success. 
The  researches  of  Whitman,  Wilson,  Conklin,  Kofoid,  Lillie, 
Mead,  and  Castle  have  given  us  the  history  of  the  origin  of 
the  germ-layers,  cell  by  cell,  in  a  variety  of  animal  forms. 
These  studies  have  shown  that  there  is  a  lack  of  uniformity 
in  the  origin  of  at  least  the  middle  layer,  and  therefore 
there  can  be  no  strict  homology  of  its  derivatives.  This 
makes  it  apparent  that  the  earlier  generalizations  of  the 
germ-layer  theory  were  too  sweeping,  and,  as  a  result,  the 
theory  is  retained  in  a  much  modified  form. 

Theoretical  Discussions. — Certain  theoretical  discus- 
sions, based  on  embryological  studies,  have  been  rife  in  recent 
years.  And  it  is  to  be  recognized  without  question  that  dis- 
cussions regarding  heredity,  regeneration,  the  nature  of  the 
developmental  process,  the  question  of  inherited  organiza- 
tion within  the  egg,  of  germinal  continuity,  etc.,  have  done 
much  to  advance  the  subject  of  embryolog}\ 

Embryology  is  one  of  the  three  great  departments  of 
biology  which,  taken  in  combination,  supply  us  with  a  knowl- 
edge of  living  forms  along  lines  of  structure,  function,  and 
development.  The  embiyological  method  of  study  is  of  in- 
creasing importance  to  comparative  anatomy  and  physiology. 
Formerly  it  was  entirely  structural,  but  it  is  now  becoming 
also  experimental,  and  it  will  therefore  be  of  more  service  to 


236  BIOLOGY   AND    ITS    MAKERS 

physiology.  While  it  has  a  strictly  technical  side,  the  science 
of  embryology  must  always  remain  of  interest  to  intelligent 
people  as  embracing  one  of  the  most  wonderful  processes 
in  nature — the  development  of  a  complex  organism  from  the 
single-celled  condition,  with  a  panoramic  representation  of 
all  the  intermediate  stages. 


CHAPTER  XI 

THE  CELL  THEORY— SCHLEIDEN,   SCHWANN, 
SCHULTZE 

The  recognition,  in  1838,  of  the  fact  that  all  the  various 
tissues  of  animals  and  plants  are  constructed  on  a  similar  plan 
wsis  an  important  step  in  the  rise  of  biology.  It  was  progress 
along  the  line  of  microscopical  observation.  One  can  readily 
understand  that  the  structural  analysis  of  organisms  could 
not  be  completed  until  their  elementaiy  parts  had  been  dis- 
covered. When  these  units  of  structure  were  discovered 
they  were  called  cells — from  a  misconception  of  their  nature — 
and,  although  the  misconception  has  long  since  been  cor- 
rected, they  still  retain  this  historical  but  misleading  name. 

The  doctrine  that  all  tissues  of  animals  and  plants  are 
composed  of  aggregations  of  these  units,  and  the  derivatives 
from  the  same,  is  known  as  the  cell-theory.  It  is  a  general- 
ization which  unites  all  animals  and  plants  on  the  broad  plane 
of  similitude  of  structure,  and,  when  we  consider  it  in  the 
light  of  its  consequences,  it  stands  out  as  one  of  the  great 
scientific  achievements  of  the  nineteenth  century.  There  is 
little  danger  of  overestimating  the  importance  of  this  doctrine 
as  tending  to  unify  the  knowledge  of  living  organisms. 

Vague  Foreshado wings  of  the  Cell-Theory. — In  attempt- 
ing to  trace  the  growth  of  this  idea,  as  based  on  actual  observa- 
tions, we  first  encounter  vague  foreshadowings  of  it  in  the 
seventeenth  and  the  eighteenth  centuries.  The  cells  were 
seen  and  sketched  by  many  early  observers,  but  were  not 
understood. 

237 


238 


BIOLOGY    AND    ITS    MAKERS 


As  long  ago  as  1665  Robert  Hooke,  the  great  English 
microscopist,  observed  the  cellular  construction  of  cork,  and 
described  it  as  made  up  of  "  little  boxes  or  cells  distinguished 
from  one  another."  He  made  sketches  of  the  appearance  of 
this  plant  tissue;  and,  inasmuch  as  the  drawings  of  Hooke 
are  the  earliest  ones  made  of  cells,  they  possess  especial  in- 


FiG.   72. — The    Earliest    Known    Picture    of   Cells   from    Hooke 's 
Micrographia  (1665).     From  the  edition  of  1780. 


terest  and  consequently  are  reproduced  here.  Fig.  72,  taken 
from  the  Micrographia,  shows  this  earliest  drawing  of  Hooke. 
He  made  thin  sections  with  a  sharp  penknife;  "and  upon 
examination  they  were  found  to  be  all  cellular  or  porous  in 
the  manner  of  a  honeycomb,  but  not  so  regular." 

We  must  not  completely  overlook  the  fact  that  Aristotle 
(384-322  B.C.)  and  Galen  (130-20C  a.d.),  those  profound 
thinkers  on  anatomical  structure,  had  reached  the  theoretical 
position  ''that  animals  and  plants,  complex  as  they  may 


THE    CELL  THEORY 


239 


appear,  are  yet  composed  of  comparatively  few  elementary 
parts,  frequently  repeated";  but  we  are  not  especially  con- 
cerned with  the  remote  history  of  the  idea,  so  much  as  with 
the  principal  steps  in  its  development  after  the  beginning  of 
microscopical  observations. 

Pictures   of   Cells   in   the   Seventeenth   Century. — ^The 
sketches  illustrating  the  microscopic  observations  of  Malpighi, 


Fig.   73.— Sketch   from    Malpighi 's   Treatise   on   the    Anatomy  of 
Plants  (1670). 


Leeuwenhoek,  and  Grew  show  so  many  pictures  of  the  cel- 
lular construction  of  plants  that  one  who  views  them  for  the 
first  time  is  struck  with  surprise,  and  might  readily  exclaim: 
''Here  in  the  seventeenth  century  we  have  the  foundation  of 
the  cell-theory."  But  these  drawings  were  merely  faithful 
representations  of  the  appearance  of  the  fabric  of  plants; 


240  BIOLOGY    AND    ITS    MAKERS 

the  cells  were  not  thought  of  as  uniform  elements  of  organic 
architecture,  and  no  theory  resulted.  It  is  true  that  Malpighi 
understood  that  the  cells  were  separable  ''utricles,"  and  that 
plant  tissue  was  the  result  of  their  union,  but  this  was  only 
an  initial  step  in  the  direction  of  the  cell-theory,  which,  as 
we  shall  see  later,  was  founded  on  the  supposed  identity  in 
development  of  cells  in  animals  and  plants.  Fig.  73  show^s 
a  sketch,  made  by  Malpighi  about  1670,  illustrating  the  micro- 
scopic structure  of  a  plant.  This  is  similar  to  the  many 
drawings  of  Grew  and  Leeuwenhoek  illustrating  the  struc- 
ture of  plant  tissues. 

Wolff. — Nearly  a  century  after  the  work  of  Malpighi,  we 
find  Wolff,  in  1759,  proposing  a  theory  regarding  the  organ- 
ization of  animals  and  plants  based  upon  observations  of 
their  mode  of  development.  He  was  one  of  the  most  acute 
scientific  observers  of  the  period,  and  it  is  to  be  noted  that  his 
conclusions  regarding  structure  were  all  founded  upon  what  he 
was  able  to  see;  while  he  gives  some  theoretical  conclusions 
of  a  purely  speculative  nature,  Wolff  was  careful  to  keep 
these  separate  from  his  observations.  The  purpose  of  his 
investigations  was  to  show  that  there  was  no  pre-formation 
in  the  embryo;  but  in  getting  at  the  basis  of  this  question,  he 
worked  out  the  identity  of  structure  of  plants  and  animals 
as  shown  by  their  development.  In  his  famous  publication 
on  the  Theor}^  of  Development  ( Theoria  Generationis)  he  used 
both  plants  and  animals. 

Huxley  epitomjzes  Wolff's  views  on  the  development  of 
elementary  parts  as  follows:  ''Every  organ,  he  says,  is  com- 
posed at  first  of  a  little  mass  of  clear,  viscous,  nutritive  fluid, 
w^hich  possesses  no  organization  of  any  kind,  but  is  at  most 
composed  of  globules.  In  this  semifluid  mass  cavities 
(Bldschen,  Zellen)  are  now  developed ;  these,  if  they  remain 
round  or  polygonal,  become  the  subsequent  cells;  if  they 
elongate,  the  vessels ;  and  the  process  is  identically  the  same, 


THE    CELL   THEORY  241 

whether  it  is  examined  in  the  vegetating  point  of  a  plant,  or 
in  the  young  budding  organs  of  an  animal." 

Wolff  was  contending  against  the  doctrine  of  pre-forma- 
tion  in  the  embryo  (see  further  under  the  chapter  on  Embry- 
ology), but  on  account  of  his  acute  analysis  he  should  be 
regarded,  perhaps,  as  the  chief  forerunner  of  the  founders  of 
the  cell-theory.  He  contended  for  the  same  method  of  de- 
velopment that  was  afterward  emphasized  by  Schleiden  and 
Schwann.  Through  the  opposition  of  the  illustrious  physi- 
ologist Haller  his  work  remained  unappreciated,  and  was 
finally  forgotten,  until  it  was  revived  again  in  181 2. 

We  can  not  show  that  Wolff's  researches  had  any  direct  in- 
fluence in  leading  Schleiden  and  Schwann  to  their  announce- 
ment of  the  cell-theory.  Nevertheless,  it  stands,  intellectually, 
in  the  direct  line  of  development  of  that  idea,  while  the  views 
of  Haller  upon  the  construction  of  organized  beings  are  a 
side-issue.  Haller  declared  that  "the  solid  parts  of  animals 
and  vegetables  have  this  fabric  in  common,  that  their  ele- 
ments are  either  fibers  or  unorganized  concrete."  This 
formed  the  basis  of  the  fiber-theory,  which,  on  account  of  the 
great  authority  of  Haller  in  physiology,  occupied  in  the 
accumulating  writings  of  anatomists  a  greater  place  than 
the  views  of  Wolff. 

Bichat,  although  he  is  recognized  as  the  founder  of  his- 
tology, made  no  original  observations  on  the  microscopic  units 
of  the  tissues.  He  described  very  minutely  the  membranes 
in  the  bodies  of  animals,  but  did  not  employ  the  microscope 
in  his  investigations. 

Oken. — In  the  work  of  the  dreamer  Oken  (i 779-1851), 
the  great  representative  of  the  German  school  of  ''Natur- 
philo Sophie,''''  we  find,  about  1808,  a  very  noteworthy  state- 
ment to  the  effect  that  "animals  and  plants  are  throughout 
nothing  else  than  manifoldly  divided  or  repeated  vesicles,  as 
I  shall  prove  anatomically  at  the  proper  time."  This  is 
16 


242  BIOLOGY    AND    ITS    MAKERS 

apparently  a  concise  statement  of  the  cell-idea  prior  to 
Schleiden  and  Schwann;  but  we  know  that  it  was  not 
founded  on  observation.  Oken,  as  was  his  wont,  gave  rein 
to  his  imagination,  and,  on  his  part,  the  idea  was  entirely 
theoretical,  and  amounted  to  nothing  more  than  a  lucky  guess. 

Haller's  fiber-theory  gave  place  in  the  last  part  of  the 
eighteenth  century  to  the  theory  that  animals  and  plants  are 
composed  of  globules  and  formless  material,  and  this  globular 
theory  was  in  force  up  to  the  time  of  the  great  generalization 
of  Schleiden  and  Schwann.  It  was  well  expounded  by  Milne- 
Edwards  in  1823,  and  now  we  can  recognize  that  at  least 
some  of  the  globules  which  he  described  were  the  nucleated 
cells  of  later  writers. 

The  Announcement  of  the  Cell-Theory. — ^We  are  now  ap- 
proaching the  time  when  the  cell-theory  was  to  be  launched. 
During  the  first  third  of  the  nineteenth  century  there  had  ac- 
cumulated a  great  mass  of  separate  observations  on  the  mi- 
croscopic structure  of  both  animals  and  plants.  For  several 
years  botanists,  in  particular,  had  been  observing  and  writing 
about  cells,  and  interest  in  these  structures  Vv^as  increasing. 
*' We  must  clearly  recognize  the  fact  that  for  some  time  prior 
to  1838  the  cell  had  come  to  be  quite  universally  recognized 
as  a  constantly  recurring  element  in  vegetable  and  animal 
tissues,  though  little  importance  was  attached  to  it  as  an 
element  of  organization,  nor  had  its  character  been  clearly 
determined  "  (Tyson). 

Then,  in  1838,  came  the  ''master-stroke  in  generaliza- 
tion "  due  to  the  combined  labors  of  two  friends,  Schleiden 
and  Schwann.  But,  although  these  two  men  are  recognized 
as  co-founders,  they  do  not  share  honors  equally;  the  work 
of  Schwann  was  much  more  comprehensive,  and  it  was  he 
who  first  used  the  term  cell-theory,  and  entered  upon  the 
theoretical  considerations  which  placed  the  theory  before  the 
scientific  world. 


THE    CELL   THEORY  243 

Schleiden  was  educated  as  a  lawyer,  and  began  the  prac- 
tice of  that  profession,  but  his  taste  for  natural  science  was 
so  pronounced  that  when  he  was  twenty-seven  years  old 
he  deserted  law,  and  went  back  to  the  university  to  study 
medicine.  After  graduating  in  medicine,  he  devoted  himself 
mainly  to  botany.  He  saw  clearly  that  the  greatest  thing 
needed  for  the  advancement  of  scientific  botany  was  a  study 
of  plant  organization  from  the  standpoint  of  development. 
Accordingly  he  entered  upon  this  work,  and,  in  1837,  arrived 
at  a  new  view  regarding  the  origin  of  plant  cells.  It  must 
be  confessed  that  this  new  view  was  founded  on  erroneous 
observations  and  conclusions,  but  it  was  revolutionary,  and 
ser\'ed  to  provoke  discussion  and  to  awaken  observation. 
This  was  a  characteristic  feature  of  Schleiden's  influence  upon 
botany.  His  work  acted  as  a  ferment  in  bringing  about  new 
activity. 

The  discovery  of  the  nucleus  in  plant  cells  by  Robert 
Brown  in  1831  was  an  important  preliminary  step  to  the  work 
of  Schleiden,  since  the  latter  seized  upon  the  nucleus  as  the 
starting-point  of  new  cells.  He  changed  the  name  of  the 
nucleus  to  cytoblast,  and  supposed  that  the  new  cell  started 
as  a  small  clear  bubble  on  one  side  of  the  nucleus,  and  by 
continued  expansion  grew  into  the  cell,  the  nucleus,  or 
cytoblast,  becoming  encased  in  the  cell-wall.  All  this  was 
shown  by  Nageli  and  other  botanists  to  be  wrong;  yet,  curi- 
ously enough,  it  was  through  the  help  of  these  false  observa- 
tions that  Schwann  arrived  at  his  general  conclusions. 

Schleiden  was  acquainted  with  Schwann,  and  in  October, 
1838,  while  the  two  were  dining  together,  he  told  Schwann 
about  his  observations  and  theories.  He  mentioned  in  par- 
ticular the  nucleus  and  its  relationship  to  the  other  parts  of 
the  cell.  Schwann  was  immediately  struck  v/ith  the  simi- 
larity between  the  observations  of  Schleiden  and  certain  of  his 
own  upon  animal  tissues.     Together  they  went  to  his  labo- 


244  BIOLOGY   AND    ITS    MAKERS 

ratoryand  examined  the  sections  of  the  dorsal  cord,  the  par- 
ticular structure  upon  which  Schwann  had  been  working. 
Schleiden  at  once  recognized  the  nuclei  in  this  structure  as 
being  similar  to  those  which  he  had  observed  in  plants,  and 
thus  aided  Schwann  to  come  to  the  conclusion  that  the  ele- 
ments in  animal  tissues  were  practically  identical  with  those  in 
plant  tissues. 

Schwann. — ^The  personalities  of  the  co-founders  of  the 
cell-theory  are  interesting.  Schwann  was  a  man  of  gentle, 
pacific  disposition,  who  avoided  all  controversies  aroused  by 
his  many  scientific  discoveries.  In  his  portrait  (Fig.  74)  we  see 
a  man  whose  striking  qualities  are  good -will  and  benignity. 
His  friend  Henle  gives  this  description  of  him :  "He  was  a  man 
of  stature  below  the  medium,  with  a  beardless  face,  an  almost 
infantile  and  always  smiling  expression,  smooth,  dark-brown 
hair,  wearing  a  fur-trimmed  dressing-gown,  living  in  a  poorly 
lighted  room  on  the  second  floor  of  a  restaurant  which  was 
not  even  of  the  second  class.  He  would  pass  whole  days 
there  without  going  out,  with  a  few  rare  books  around  him, 
and  numerous  glass  vessels,  retorts,  vials,  and  tubes,  simple 
apparatus  which  he  made  himself.  Or  I  go  in  imagina- 
tion to  the  dark  and  fusty  halls  of  the  Anatomical  Institute 
w^here  we  used  to  w^ork  till  nightfall  by  the  side  of  our  excellent 
chief,  Johann  M tiller.  We  took  our  dinner  in  the  evening, 
after  the  English  fashion,  so  that  we  might  enjoy  more  of  the 
advantages  of  daylight." 

Schwann  drew  part  of  his  stimulus  from  his  great  master, 
Johannes  Miiller.  He  was  associated  with  him  as  a  student, 
first  in  the  University  of  Wiirzburg,  where  Miiller,  with  rare 
discernment  for  recognizing  genius,  selected  Schwann  for 
especial  favors  and  for  close  personal  friendship.  The  influ- 
ence of  his  long  association  with  Miiller,  the  greatest  of  all 
trainers  of  anatomists  and  physiologists  of  the  nineteenth 
century,  must  have  been  very  uplifting.     A  few  years  later, 


THE    CELL   THEORY 


245 


Schwann  found  himself  at  the  University  of  Berlin,  where 
Miiller  had  been  called,  and  he  became  an  assistant  in  the 
master's  laboratory.  There  he  gained  the  powerful  stimulus 
of  constant  association  with  a  great  personality. 


Fig.   74. — Theodor  Schwann,   1810-1882. 


In  1839,  just  after  the  publication  of  his  work  on  the  cell- 
theory,  Schwann  was  called  to  a  professorship  in  the  Univer- 
sity of  Louvain,  and  after  remaining  there  nine  years,  was 
transferred  to  the  University  of  Liege.     He  was   highly  re- 


246  BIOLOGY   AND    ITS    MAKERS 

spected  in  the  university,  and  led  a  useful  life,  although  after 
going  to  Belgium  he  published  only  one  work — that  on  the 
uses  of  the  bile.     He  was  recognized  as  an  adept  experi- 


FlG.    75. M.    SCHLEIDEN,    1804-1881. 

menter  and  demonstrator,  and  "clearness,  order,  and  method  '* 

are  designated  as  the  characteristic  qualities  of  his  teaching. 

His  announcement  of  the  cell-theory  was  his  most  impor- 


THE    CELL   THEORY  247 

tant  work.  Apart  from  that  his  best -known  contributions  to 
science  are:  experiments  upon  spontaneous  generation,  his 
discovery  of  the  "  sheath  of  Schwann,"  in  nerve  fibers,  and 
his  theory  of  fermentation  as  produced  by  microbes. 

Schleiden.— Schleiden  (Fig.  75)  was  quite  different  in 
temperament  from  Schwann.  He  did  not  have  the  fine  self- 
control  of  Schwann,  but  was  quick  to  take  up  the  gauntlet 
and  enter  upon  controversies.  In  his  caustic  replies  to  his 
critics,  he  indulged  in  sharp  personalities,  and  one  is  at  times 
inclined  to  suspect  that  his  early  experience  as  a  lawyer  had 
something  to  do  with  his  method  of  handling  opposition. 
With  all  this  he  had  correct  ideas  of  the  object  of  scientific 
study  and  of  the  methods  to  be  used  in  its  pursuit.  He  in- 
sisted upon  observation  and  experiment,  and  upon  the  neces- 
sity of  studying  the  development  of  plants  in  order  to  under- 
stand their  anatomy  and  physiology.  He  speaks  scornfully 
of  the  botany  of  mere   species-making  as  follows: 

'^  Most  people  of  the  world,  even  the  most  enlightened,  are 
still  in  the  habit  of  regarding  the  botanist  as  a  dealer  in  bar- 
barous Latin  names,  as  a  man  who  gathers  flowers,  names 
them,  dries  them,  and  wraps  them  in  paper,  and  all  of  whose 
wisdom  consists  in  determining  and  classifying  this  hay 
which  he  has  collected  with  such  great  pains." 

Although  he  insisted  on  correct  micthods,  his  ardent  nature 
led  him  to  champion  conclusions  of  his  own  before  they  were 
thoroughly  tested.  His  great  influence  in  the  development 
of  scientific  botany  lay  in  his  earnestness,  his  application  of 
new  methods,  and  his  fearlessness  in  drawing  conclusions, 
which,  although  frequently  wrong,  formed  the  starting-point 
of  new^  researches. 

Let  us  now  examine  the  original  publications  upon  which 
the  cell-theory  was  founded. 

Schleiden*s  Contribution. — Schleiden's  paper  was  par- 
ticularly directed  to  the  question.  How  does  the  cell  originate? 


248  BIOLOGY   AND    ITS    MAKERS 

and  was  published  in  MuUer's  ArchiVj  in  1838,  under  the 
German  title  of  Ueber  Phylogenesis.  As  stated  above,  the 
cell  had  been  recognized  for  some  years,  but  the  question  of 
its  origin  had  not  been  investigated.  Schleiden  says :  ''  I  may 
omit  all  historical  introduction,  for,  so  far  as  I  am  acquainted. 
no  direct  observations  exist  at  present  upon  the  development 
of  the  cells  of  plants." 

He  then  goes  on  to  define  his  view  of  the  nucleus  (cyto- 
blast)  and  of  the  development  of  the  cell  around  it,  saying: 
"  As  soon  as  the  cytoblasts  have  attained  their  full  size,  a 
delicate  transparent  vesicle  arises  upon  their  surface.  This 
is  the  young  cell."  As  to  the  position  of  the  nucleus  in  the 
fully  developed  cell,  he  is  very  explicit:  "It  is  evident,"  he 
says,  "  from  the  foregoing  that  the  cytoblast  can  never  lie 
free  in  the  interior  of  the  cell,  but  is  always  enclosed  in  the 
cell- wall,"  etc. 

Schleiden  fastened  these  errors  upon  the  cell-theory,  since 
Schwann  relied  upon  his  observations.  On  another  point  of 
prime  importance  Schleiden  was  wrong:  he  regarded  all  new 
cell-formation  as  the  formation  of  "cells  within  cells,"  as  dis- 
tinguished from  cell-division,  as  we  now  know  it  to  take  place. 

Schleiden  made  no  attempt  to  elaborate  his  views  into  a 
comprehensive  cell-theory,  and  therefore  his  connection  as 
a  co-founder  of  this  great  generalization  is  chiefly  in  paving 
the  way  and  giving  the  suggestion  to  Schwann,  which  enabled 
the  latter  to  establish  the  theory.  Schleiden's  paper  occupies 
some  thirty-two  pages,  and  is  illustrated  by  two  plates.  He 
was  thirty-four  years  old  when  this  paper  was  published,  and 
directly  afterward  was  called  to  the  post  of  adjunct  professor 
of  botany  in  the  University  of  Jena,  a  position  which  with 
promotion  to  the  full  professorship  he  occupied  for  twenty- 
three  years. 

Schwann's  Treatise. — In  1838,  Schwann  also  announced 
his  cell-theory  in  a  concise  form  in  a  German  scientific  period- 


THE    CELL   THEORY  249 

ical,  and,  later,  to  the  Paris  Academy  of  Sciences;  but  it  was 
not  till  1 839  that  the  fully  illustrated  account  was  published. 
This  treatise  with  the  cumbersome  title,  ''Microscopical 
Researches  into  the  Accordance  in  the  Structure  and  Growth 
of  Animals  and  Plants"  (Mikroscopische  Untersuchungenuher 
die  Uebereinstimmung  in  der  Structur  und  dem  Wachsthum 
der  Thiere  und  Pflanzen)  takes  rank  as  one  of  the  great  classics 
in  biology.  It  fills  215  octavo  pages,  and  is  illustrated  with 
four  plates. 

"The  purpose  of  his  researches  was  to  prove  the  identity 
of  structure,  as  shown  by  their  development,  between  animals 
and  plants."  This  is  done  by  direct  comparisons  of  the  ele- 
mentary parts  in  the  two  kingdoms  of  organic  nature. 

His  writing  in  the  "Microscopical  Researches"  is  clear 
and  philosophical,  and  is  divided  into  three  sections,  in  the 
first  two  of  which  he  confines  himself  strictly  to  descriptions 
of  observations,  and  in  the  third  part  of  which  he  enters  upon 
a  philosophical  discussion  of  the  significance  of  the  observa- 
tions. He  comes  to  the  conclusion  that  "the  elementary 
parts  of  all  tissues  are  formed  of  cells  in  an  analogous,  though 
very  diversified  manner,  so  that  it  may  be  asserted  that  there 
is  one  universal  principle  of  development  for  the  elementary 
parts  of  organisms,  however  different,  and  that  this  principle 
is  the  formation  of  cells." 

It  was  in  this  treatise  also  that  he  made  use  of  the  term 
cell-theory,  as  follows:  "The  development  of  the  proposition 
that  there  exists  one  general  principle  for  the  formation  of  all 
organic  productions,  and  that  this  principle  is  the  formation 
of  cells,  as  well  as  the  conclusions  which  may  be  drawn  from 
this  proposition,  may  be  comprised  under  the  term  cell-theory j 
using  it  in  its  more  extended  signification,  while,  in  a  more 
limited .  sense,  by  the  theory  of  cells  .we  understand  whatever 
mxay  be  inferred  from  this  proposition  with  respect  to  the 
powers  from  which  these  phenomena  result." 


250  BIOLOGY    AND    ITS    MAKERS 

One  comes  from  the  reading  of  these  two  contributions 
to  science  with  the  feeling  that  it  is  really  Schwann's  cell- 
theor)',  and  that  Schleiden  helped  by  lighting  the  way  that 
his  fellow- worker  so  successfully  trod. 

Modification  of  the  Cell-Theory. — ^The  form  in  which  the 
cell- theory  was  given  to  the  world  by  Schleiden  and  Schwann 
was  very  imperfect,  and,  as  already  pointed  out,  it  contained 
fundamental  errors.  The  founders  of  the  theory  attached 
too  much  importance  to  the  cell -wall,  and  they  described  the 
cell  as  a  hollow  cavity  bounded  by  walls  that  were  formed 
around  a  nucleus.  They  were  wrong  as  to  the  mode  of  the 
development  of  the  cell,  and  as  to  its  nature.  Nevertheless, 
the  great  truth  that  all  parts  of  animals  and  plants  are  built 
of  similar  units  or  structures  was  well  substantiated.  This 
remained  a  permanent  part  of  the  theory,  but  all  ideas  re- 
garding the  nature  of  the  units  were  profoundly  altered. 

In  order  to  perceive  the  line  along  which  the  chief  modifi- 
cations were  made  we  must  take  account  of  another  scientific 
advance  of  about  the  same  period.  This  was  the  discovery 
of  protoplasm,  an  achievement  which  takes  rank  with  the 
advances  of  greatest  importance  in  biology,  and  has  proved 
to  be  one  of  the  great  events  of  the  nineteenth  century. 

The  Discovery  of  Protoplasm  and  its  Effect  on  the  Cell- 
Theory. — In  1835,  before  the  announcement  of  the  cell- 
theory,  living  matter  had  been  observed  by  Dujardin.  In 
lower  animal  forms  he  noticed  a  semifluid,  jelly-like  sub- 
stance, which  he  designated  sarcode,  and  which  he  described 
as  being  endowed  with  all  the  qualities  of  life.  The  same 
semifluid  substance  had  previously  caught  the  attention  of 
some  observ^ers,  but  no  one  had  as  yet  announced  it  as  the 
actual  living  part  of  organisms.  Schleiden  had  seen  it  and 
called  it  gum.  Dujardin  was  far  from  appreciating  the  full 
importance  of  his  discover}-,  and  for  a  long  time  his  descrip- 
tion of  sarcode  remained  separate;   but  in  1846  Hugo  von 


THE    CELL   THEORY  251 

Mohl,  a  botanist,  observed  a  similar  jelly-like  substance  in 
plants,  which  he  called  plant  schleim,  and  to  which  he  attached 
the  name  protoplasma. 

The  scientific  world  was  now  in  the  position  of  recogniz- 
ing living  substance,  which  had  been  announced  as  sarcode 
in  lower  animals,  and  as  protoplasm  in  plants;  but  there 
was  as  yet  no  clear  indication  that  these  two  substances 
were  practically  identical.  Gradually  there  came  stealing 
into  the  minds  of  observers  the  suspicion  that  the  sarcode  of 
the  zoologists  and  the  protoplasm  of  the  botanists  were  one 
and  the  same  thing.  This  proposition  was  definitely  main- 
tained by  Cohn  in  1850,  though  with  him  it  was  mainly 
theoretical,  since  his  observations  were  not  sufficiently  ex- 
tensive and  accurate  to  support  such  a  conclusion. 

Eleven  years  later,  however,  as  the  result  of  extended 
researches,  Max  Schultze  promulgated,  in  1861,  the  proto- 
plasm doctrine,  to  the  effect  that  the  units  of  organization 
consist  of  little  masses  of  protoplasm  surrounding  a  nucleus, 
and  that  this  protoplasm,  or  living  substance,  is  practically 
identical  in  both  plants  and  animals. 

The  effect  of  this  conclusion  upon  the  cell-theory  was 
revolutionary.  During  the  time  protoplasm  was  being  ob- 
served the  cell  had  likewise  come  under  close  scrutiny,  and 
naturalists  had  now  an  extensive  collection  of  facts  upon 
which  to  found  a  theory.  It  has  been  shown  that  many 
animal  cells  have  no  cell-wall,  and  the  final  conclusion  was 
inevitable  that  the  essential  part  of  a  cell  is  the  semifluid 
living  substance  that  resides  within  the  cavity  when  a  cell- 
wall  is  present.  Moreover,  when  the  cell-wall  is  absent,  the 
protoplasm  is  the  "cell."  The  position  of  the  nucleus  was 
also  determined  to  be  within  the  living  substance,  and  not, 
as  Schleiden  had  maintained,  within  the  cell-wall.  The 
definition  of  Max  Schultze,  that  a  cell  is  a  globule  of  proto- 
plasm surrounding  a  nucleus,  marks  a  new  era  in  the  cell- 


252  BIOLOGY   x\ND    ITS    MAKERS 

theory,  in  which  the  original  generalization  became  consoli- 
dated with  the  protoplasm  doctrine. 

Further  Modifications  of  the  Cell-Theory. — ^The  reformed 
cell-theory  was,  however,  destined  to  undergo  further  modifi- 
cation, and  to  become  greatly  extended  in  its  application. 
At  first  the  cell  was  regarded  merely  as  an  element  of  struc- 
ture; then,  as  a  supplement  to  this  restricted  view,  came  the 
recognition  that  it  is  also  a  unit  of  physiology,  viz.,  that  all 
physiological  activities  take  place  within  the  cell.  Matters 
did  not  come  to  a  rest,  however,  with  the  recognition  of  these 
two  fundamental  aspects  of  the  cell.  The  importance  of  the 
cell  in  development  also  took  firmer  hold  upon  the  minds  of 
anatomists  after  it  was  made  clear  that  both  the  egg  and  its 
fertilizing  agents  are  modified  cells  of  the  parent's  body.  It 
was  necessary  to  comprehend  this  fact  in  order  to  get  a  clear 
idea  of  the  origin  of  cells  within  the  body  of  a  multicellular 
organism,  and  of  the  relation  between  the  primordial  element 
and  the  fully  developed  tissues.  Finally,  when  observ^ers 
found  within  the  nucleus  the  bearers  of  hereditary  qualities, 
they  began  to  realize  that  a  careful  study  of  the  behavior  of 
the  cell  elements  during  development  is  necessar}^  for  the 
investigation  of  hereditary  transmissions. 

A  statement  of  the  cell-theory  at  the  present  time,  then, 
must  include  these  four  conceptions:  the  cell  as  a  unit  of 
structure,  the  cell  as  a  unit  of  physiological  activity,  the  cell 
as  embracing  all  hereditary  qualities  within  its  substance, 
and  the  cell  in  the  historical  development  of  the  organism. 

Some  of  these  relations  may  now  be  more  fully  illustrated. 

Origin  of  Tissues. — ^The  egg  in  which  all  organisms  above 
the  very  lowest  begin,  is  a  single  cell  having,  under  the  micro- 
scope, the  appearance  shown  in  Fig.  76.  After  fertilization, 
this  divides  repeatedly,  and  many  cohering  cells  result.  The 
cells  are  at  first  similar,  but  as  they  increase  in  number,  and 
as  development  proceeds,  they  grow  different,  and  certain 


THE    CELL    THEORY 


253 


groups  are  set  apart  to  perform  particular  duties.  The  divi- 
sion of  physiological  labor  which  arises  at  this  time  m.arks 
the  beginning  of  separate  tissues.  It  has  been  demonstrated 
over  and  over  that  all  tissues  are  composed  of  cells  and  cell- 
products,  though  in  some  instances  they  are  much  modified. 
The  living  cells  can  be  seen  even  in  bone  and  cartilage,  in 


Fig.  76. — ^The  Egg  and  Early  Stages  in  its  Development. 
(After  Gegenbaur.) 


which  they  are  separated  by  a  lifeless  matrix,  the  latter  being 
the  product  of  cellular  activity. 

Fig.  77  shows  a  stage  in  the  development  of  one  of  the 
mollusks  just  as  the  differentiation  of  cells  has  commenced. 

The  Nucleus. — ^To  the  earlier  observers  the  protoplasm 
appeared  to  be  a  structureless,  jelly-like  mass  containing 
granules  and  vacuoles;  but  closer  acquaintance  with  it  has 
shown  that  it  is  in  reality  very  complex  in  structure  as  well 
as  in  chemical  composition.  It  is  by  no  means  homogeneous; 
adjacent  parts  are  different  in  properties  and  aptitudes.  The 
nucleus,  which  is  more  readily  seen  than  other  cell  elements, 


254  BIOLOGY    AND    ITS    MAKERS 

was  shown  to  be  of  great  importance  in  cell-life — to  be  a 
structure  which  takes  the  lead  in  cell  division,  and  in  general 
dominates  the  rest  of  the  protoplasm. 

Chromosomes. — After  dyes  came  into  use  for  staining  the 
protoplasm  (1868),  it  became  evident  that  certain  parts  of  it 
stain  deeply,  while  other  parts  stain  faintly  or  not  at  all.  This 
led  to  the  recognition  of  protoplasm  as  made  up  of  a  densely 
staining  portion  called  chromatin,  and  a  faintly  staining  por- 


FiG.  77. — An  Early  Stage  in  the  Development  of  the  Egg  of  a  Rock- 
Limpet.      (After  Conklin.) 

tion  designated  achromatin.  This  means  of  making  different 
parts  of  protoplasm  visible  under  the  microscope  led  to  im- 
portant results,  as  when,  in  1883,  it  was  discovered  that  the 
nucleus  contains  a  definite  number  of  small  (usually  rod- 
shaped)  bodies,  which  become  evident  during  nuclear  divi- 
sion, and  play  a  wonderful  part  in  that  process.  These  bodies 
take  the  stain  more  deeply  than  other  components  of  the 
nucleus,  and  are  designated  chromosomes. 

Attention  having  been  directed  to  these   little  bodies, 
continued  observations  showed  that,  although  they  vary  in 


THE    CELL   THEORY 


255 


number — commonly  from  two  to  twenty -four — in  different 
parts  of  animals  and  plants,  they  are,  nevertheless,  of  the 
same  number  in  all  the  cells  of  any  particular  plant  or  ani- 


Fig.  78. — Highly  Magnified  Tissue  Cells  from  the  Skin  of  a 
Salamander  in  an  Active  State  of  Growth.  Dividing  cells  with 
chromosomes  are  shown  at  a,  b,  and  c,.     (After  Wilson.) 


mal.  As  a  conclusion  to  this  kind  of  observation,  it  needs 
to  be  said  that  the  chromosomes  are  regarded  as  the  actual 
bearers  of  hereditary  cjualities.     The  chromosomes  do  not 


256 


BIOLOGY    AND    ITS    MAKERS 


show  in   resting-stages  of   the  nucleus;    their  substance  is 
present,  but  is  not  aggregated  into  the  form  of  chromosomes. 
Fig.  78  shows  tissue  cells,  some  of  which  are  in  the  divid- 
ing and  others  in  the  resting-stage.     The  nuclei  in  process  of 


C 


\r 


is     \ 


cM 


^^\li/  , 


SHKIi 


r^A 


Fig.  79. — Diagram  of  the  Chief  Steps  in  Cell-division. 
(After  Parker  as  altered  from  Flemming.) 

division  exhibit  the  rod-like  chromosomes,  as  shown  at  a, 
J,  and  c. 

Centrosome. — ^The  discovery  (1876)  of  a  minute  spot  of 
deeply  staining  protoplasm,  usually  just  outside  the  nuclear 


THE    CELL   THEORY 


257 


membrane,  is  another  illustration  of  the  complex  structure 
of  the  cell.  Although  the  ccntrosome,  as  this  spot  is  called, 
has  been  heralded  as  a  dynamic  agent,  there  is  not  complete 
agreement  as  to  its  purpose,  but  its  presence  makes  it  necess- 
sary  to  include  it  in  the  definition  of  a  cell. 

The  Cell  in  Heredity. — The  problems  of  inheritance,  in 
so  far  as  they  can  be  elucidated  by  structural  studies,  have 
come  to  be  recognized  as  problems  of  cellular  life.  But  we 
cannot  understand  what  is  implied  by  this  conclusion  without 
referring  to  the  behavior  of  the  chromosomes  during  cell- 
division.  This  is  a  very  complex  process,  and  varies  som.e- 
what  in  different  tissues.  We  can, 
however,  with  the  help  of  Fig.  79, 
describe  what  takes  place  in  a  typical 
case.  The  nucleus  does  not  divide 
directly,  but  the  chromosomes  congre- 
gate around  the  equator  of  a  spindle 
(D)  formed  from  the  achromatin;  they 
then  undergo  division  lengthwise,  and 
migrate  to  the  poles  (E,  F,  G),  after 
which  a  partition  w^all  is  formed  divid- 
ing the  cell.  This  manner  of  division 
of  the  chromosomes  secures  an  equable 
partition  of  the  protoplasm.  In  the 
case  of  fertilized  eggs,  one-half  of  the 
chromosomes  are  derived  from  the 
sperm  and  one-half  from  the  egg. 
Each  cell  thus  contains  hereditary 
substance  derived  from  both  mater- 
nal and  paternal  nuclei.  This  is  briefly  the  basis  for  re- 
garding inheritance  as  a  phenomenon  of  cell-life. 

A  diagram  of  the  cell  as  now  understood  (Pig.  80)  will 
be  helpful  in  showing  how  much  the  conception  of  the  cell 
has  changed  since  the  time  of  Schleiden  and  Schwann. 
17 


Fig.  80. — Diagram 
of  a  Cell.  (Modified 
after  Wilson.) 


258  BIOLOGY   AND    ITS    MAKERS 

Definition. — The  definition  of  Verworn,  made  in  1895, 
may  be  combined  with  this  diagram:  A  cell  is  ''a  body  con- 
sisting essentially  of  protoplabm  in  its  general  form,  including 
the  unmodified  cytoplasm,  and  the  specialized  nucleus  and 
centrosome;  while  as  unessential  accompaniments  may  be 
enumerated:  (i)  the  cell  membrane,  (2)  starch  grains,  (3) 
pigment  granules,  (4)  oil  globules,  and  (5)  chlorophyll  gran- 
ules." No  definition  can  include  all  variations,  but  the  one 
quoted  is  excellent  in  directing  attention  to  the  essentials — • 
to  protoplasm  in  its  general  form,  and  the  modified  proto- 
plasmic parts  as  distinguished  from  the  unessential  accom- 
paniments, as  cell  membrane  and  cell  contents. 

The  definition  of  Verworn  was  reached  by  a  scries  of 
steps  representing  the  historical  advance  of  knowledge  regard- 
ing the  cell.  Schleiden  and  Schwann  looked  upon  the  cell 
as  a  hollow  chamber  having  a  cell-wall  which  had  been 
formed  around  the  nucleus;  it  was  a  great  step  when 
Schultze  defined  the  cell  in  terms  of  living  substance  as  "a 
globule  of  protoplasm  surrounding  a  nucleus,"  and  it  is  a 
still  deeper  level  of  analysis  which  gives  us  a  discriminating 
definition  like  that  of  Verworn. 

When  we  are  brought  to  realize  that,  in  large  part,  the 
questions  that  engage  the  mind  of  the  biologist  have  their 
basis  in  the  study  of  cells,  we  are  ready  to  appreciate  the  force 
of  the  statement  that  the  establishment  of  the  cell-theory 
was  one  of  the  great  events  of  the  nineteenth  century,  and, 
further,  that  it  stands  second  to  no  theory,  with  the  single 
exception  of  that  of  organic  evolution,  in  advancing  bio- 
logical science. 


CHAPTER  Xll 

PROTOPLASM,  THE  PHYSICAL  BASIS   OF  LIFE 

The  recognition  of  the  role  that  protoplasm  plays  in  the 
living  world  was  so  far-reaching  in  its  results  that  we  take 
up  for  separate  consideration  the  history  of  its  discovery.  Al- 
though it  is  not  yet  fifty  years  since  Max  Schultze  established 
the  protoplasm  doctrine,  it  has  already  had  the  greatest 
influence  upon  the  progress  of  biology.  To  the  consideration 
of  protoplasm  in  the  previous  chapter  should  be  added  an 
account  of  the  conditions  of  its  discovery,  and  of  the  person- 
ality and  views  of  the  men  whose  privilege  it  was  to  bring 
the  protoplasm  idea  to  its  logical  conclusion.  Before  doing 
so,  however,  we  shall  look  at  the  nature  of  protoplasm 
itself. 

Protoplasm. — ^This  substance,  which  is  the  seat  of  all 
vital  activity,  was  designated  by  Huxley  "  the  physical  basis 
of  life,"  a  graphic  expression  which  brings  before  the  mind  the 
central  fact  that  life  is  manifested  in  a  material  substratum 
by  which  it  is  conditioned.  All  that  biologists  have  been  able 
to  discover  regarding  life  has  been  derived  from  the  observa- 
tion of  that  material  substratum.  It  is  not  difficult,  with  the 
help  of  a  microscope,  to  get  a  view  of  protoplasmic  activity, 
and  that  which  was  so  laboriously  made  known  about  i860 
is  now  shown  annually  to  students  beginning  biology. 

Inasmuch  as  all  living  organisms  contain  protoplasm, 
one  has  a  wide  range  of  choice  in  selecting  the  plant  or  the 
animal  upon  which  to  make  observations. 

We  may,  for  illustration,  take  one  of  the  simplest  of  animal 
organisms,  the  amoeba,  and  place  it  under  the  high  powers 

259 


20O  BIOLOGY    AND    ITS    MAKERS 

of  the  microscope.  This  little  animal  consists  almost  entirely 
of  a  lump  of  living  jelly.  Within  the  living  substance  of 
which  its  body  is  composed  all  the  vital  activities  character- 
istic of  higher  animals  are  going  on,  but  they  are  manifested 
in  simpler  form.  These  manifestations  differ  only  in  degree 
of  development,  not  in  kind,  from  those  we  see  in  bodies  of 
higher  organisms. 

We  can  watch  the  movements  in  this  amoeba,  deter- 
mine at  first  hand  its  inherent  qualities,  and  then  draw  up 
a  sort  of  catalogue  of  its  vital  properties.  We  notice  an 
almost  continual  flux  of  the  viscid  substance,  by  means  of 
which  it  is  able  to  alter  its  form  and  to  change  its  position. 
This  quality  is  called  that  of  contractility.  In  its  essential 
nature  it  is  like  the  protoplasmic  movement  that  takes  place 
in  a  contracting  muscle.  We  find  also  that  the  substance 
of  the  amoeba  responds  to  stimulations — such  as  touching 
it  with  a  bristle,  or  heating  it,  or  sending  through  it  a  light 
electric  shock.  This  response  is  quite  independent  of  the 
contractility,  and  by  physiologists  is  designated  the  property 
of  being  irritable. 

By  further  observations  one  may  determine  that  the  sub- 
stance of  the  amoeba  is  receptive  and  assimilative,  that  it  is 
respiratory,  taking  in  oxygen  and  giving  off  carbonic  dioxide, 
and  that  it  is  also  secretor}-.  If  the  amoeba  be  watched 
long  enough,  it  may  be  seen  to  undergo  division,  thus  produc- 
ing another  individual  of  its  kind.  We  say,  therefore,  that  it 
exhibits  the  power  of  reproduction.  All  these  properties 
manifested  in  close  association  in  the  am.oeba  are  exhibited 
in  the  bodies  of  higher  organisms  in  a  greater  degree  of 
perfection,  and  also  in  separation,  particular  organs  often 
being  set  apart  for  the  performance  of  one  of  these  par- 
ticular functions.  We  should,  however,  bear  in  mind  that 
in  the  simple  protoplasm  of  the  amoeba  is  found  the  germ  of 
all  the  activities  of  the  higher  animals. 


THE   PHYSICAL   BASIS    OF    LIFE 


261 


It  will  be  convenient  now  to  turn  our  attention  to  the 
microscopic  examination  of  a  plant  that  is  sufficiently  trans- 
parent to  enable  us  to  look  within  its  living  parts  and  observe 
the  behavior  of  protoplasm.  The  first  thing  that  strikes  one 
is  the  continual  activity  of  the  living  substance  within  the 
boundaries  of  a  particular  cell.     This  movement  sometimes 


tear's  ;;?|-|  I  •'V;V;v 


Fig.  81, — (A)  Rotation  of  Protoplasm  in  the  Cells  of  Nitella. 
(B)  Highly  Magnified  Cell  of  a  Tradescantia  Plant,  Showing 
Circulation  of  Protoplasm.     (After  Sedgwick  and  Wilson.) 

takes  the  form  of  rotation  around  the  walls  of  the  cell  (Fig. 
81  A).  In  other  instances  the  protoplasm  marks  out  for  itself 
new  paths,  giving  a  more  complicated  motion,  called  circula- 
tion (Fig.  81  5).  These  movements  are  the  result  of  chemi- 
cal changes  taking  place  within  the  protoplasm,  and  they  are 
usually  to  be  observed  in  any  plant  or  animal  organism. 

Under  the  most  favorable  conditions  these  movements,  as 
seen  under  the  microscope,  make  a  perfect  torrent  of  un- 
ceasing activity,  and  introduce  us  to  one  of  the  wonderful 
sights  of  which  students  of  biology  have  so  many.     Huxley 


262  BIOLOGY    AND    ITS    MAKERS 

(with  slight  verbal  alterations)  says :  "The  spectacle  afforded 
by  the  wonderful  energies  imprisoned  within  the  compass  of 
the  microscopic  cell  of  a  plant,  which  we  commonly  regard 
as  a  merely  passive  organism,  is  not  easily  forgotten  by  one 
who  has  watched  its  movement  hour  by  hour  without  pause 
or  sign  of  weakening.  The  possible  complexity  of  many 
other  organisms  seemingly  as  simple  as  the  protoplasm  of 
the  plant  just  mentioned  dawns  upon  one,  and  the  compari- 
son of  such  activity  to  that  of  higher  animals  loses  much 
of  its  startling  character.  Currents  similar  to  these  have 
been  observed  in  a  great  multitude  of  very  different  plants, 
and  it  is  quite  uniformly  believed  that  they  occur  in  more 
or  less  perfection  in  all  young  vegetable  cells.  If  such  be 
the  case,  the  wonderful  noonday  silence  of  a  tropical  forest 
is  due,  after  all,  only  to  the  dullness  of  our  hearing,  and  could 
our  ears  catch  the  nmrmur  of  these  tiny  maelstroms  as  they 
whirl  in  the  innumerable  myriads  of  living  cells  that  con- 
stitute each  tree,  we  should  be  stunned  as  with  the  roar  of  a 
great  city." 

The  Essential  Steps  in  Recognizing  the  Likeness  of 
Protoplasm  in  Plants  and  Animals 

Dujardin. — This  substance,  of  so  much  interest  and  im- 
portance to  biologists,  was  first  clearly  described  and  dis- 
tinguished from  other  viscid  substance,  as  albumen,  by  Felix 
Dujardin  in  1835.  ^^^th  the  substance  and  the  movements 
therein  had  been  seen  and  recorded  by  others:  by  Rosel 
von  Rosenhof  in  1755  in  the  proteus  animalcule;  again  in 
1772  by  Corti  in  chara;  by  Mayen  in  1827  in  Vallisnieria; 
and  in  1831  by  Robert  Brown  in  Tradescantia.  One  of  these 
records  was  for  the  animal  kingdom,  and  three  were  for 
plants.  The  observations  of  Dujardin,  however,  were  on  a 
different  plane  from  those  of  the  earlier  naturalists,  and  he 


THE   PHYSICAL   BASIS    OF    LIFE  263 

is  usually  credited  with  being  the  discoverer  of  protoplasm. 
His  researches,  moreover,  were  closely  connected  with  the 
development  of  the  ideas  regarding  the  role  played  in  nature 
by  this  living  substance. 

Dujardin  was  a  quiet  modest  man,  whose  attainments  and 
service  to  the  progress  of  biology  have  usually  been  under- 
rated. He  was  born  in  1801  at  Tours,  and  died  in  i860  at 
Rennes.  Being  descended  from  a  race  of  watchmakers,  he 
received  in  his  youth  a  training  in  that  craft  which  cultivated 
his  natural  manual  dexterity,  and,  later,  this  assisted  him  in 
his  manipulations  of  the  microscope.  He  had  a  fondness  for 
sketching,  and  produced  some  miniatures  and  other  works 
of  art  that  showed  great  merit.  His  use  of  colors  was  very 
effective,  and  in  181 8  he  went  to  Paris  for  the  purpose  of 
perfecting  himself  in  painting,  and  with  the  intention  of 
becoming  an  artist.  The  small  financial  returns,  however, 
^'led  him  to  accept  work  as  an  engineer  directing  the  con- 
struction of  hydraulic  work  in  Sedan."  He  had  already 
shown  a  love  for  natural  science,  and  this  led  him  from  engin- 
eering into  work  as  a  librarian  and  then  as  a  teacher.  He 
made  field  observations  in  geolog}'  and  botany,  and  com- 
menced publication  in  those  departments  of  science. 

About  1834  he  began  to  devote  his  chief  efforts  to 
microscopic  work,  toward  which  he  had  a  strong  inclination, 
and  from  that  time  on  he  became  a  zoologist,  with  a  steadily 
growing  recognition  for  high-class  observation.  Besides  his 
technical  scientific  papers,  he  wrote  in  a  popular  vein  to 
increase  his  income.  Among  his  writings  of  this  type  may  be 
mentioned  as  occupying  high  rank  his  charmingly  written 
^'Rambles  of  a  Naturalist"  {Promenades  d'un  Naturaliste, 
1838). 

By  1840  he  had  established  such  a  good  record  as  a  sci- 
■entific  investigator  that  he  was  called  to  the  newly  founded 
University  of  Rennes  as  dean  of  the  faculty.     He  found  him- 


264  BIOLOGY   AND    ITS    MAKERS 

self  in  an  atmosphere  of  jealous  criticism,  largely  on  account 
of  his  being  elevated  to  the  station  of  dean,  and  after  two 
years  of  discomfort  he  resigned  the  deanship,  but  retained 
his  position  as  a  professor  in  the  university.  He  secured  a 
residence  in  a  retired  spot  near  a  church,  and  lived  there 
simply.  In  his  leisure  moments  he  talked  frequently  with 
the  priests,  and  became  a  devout  Catholic. 

His  contributions  to  science  cover  a  wide  range  of  subjects. 
In  his  microscopic  work  he  discovered  the  rhizopods  in  1834, 
and  the  study  of  their  structure  gave  him  the  key  to  that  of 
the  other  protozoa.  In  1835  he  visited  the  Mediterranean, 
where  he  studied  the  oceanic  foraminifera,  and  demonstrated 
that  they  should  be  grouped  with  the  protozoa,  and  not,  as 
had  been  maintained  up  to  that  time,  with  the  mollusca. 
It  was  during  the  prosecution  of  these  researches  that  he 
made  the  observations  upon  sarcode  that  are  of  particular 
interest  to  us. 

His  natural  history  of  the  infusoria  (1841)  makes  a  vol- 
ume of  700  pages,  full  of  original  observations  and  sketches. 
He  also  invented  a  means  of  illumination  for  the  microscope, 
and  wrote  a  manual  of  microscopic  observation.  Among  the 
ninety-six  publications  of  Dujardin  listed  by  Professor  Joubin 
there  are  seven  general  works,  twenty  relating  to  the  protozoa, 
twenty-four  to  geology,  three  to  botany,  four  to  physics, 
twenty-five  to  arthropods,  eight  to  worms,  etc.,  etc.  But  as 
Joubin  says:  "The  great  modesty  of  Dujardin  allowed  him 
to  see  published  by  others,  without  credit  to  himself,  numer- 
ous facts  and  observations  which  he  had  established."  This 
failure  to  assert  his  claims  accounts  in  part  for  the  inadequate 
recognition  that  his  work  has  received. 

No  portrait  of  Dujardin  was  obtainable  prior  to  1898. 
Somewhat  earlier  Professor  Joubin,  who  succeeded  other 
occupants  of  the  chair  which  Dujardin  held  in  the  University 
of  Rennes,  found  in  the  possession  of  his  descendants  a 


THE   PHYSICAL   BASIS   OF  LIFE  265 

portrait,  which  he  was  permitted  to  copy.     The  earliest  re- 
production of  this  picture  to  reach  this  country  came  to  the 


Fig.  82. — Felix  Dujardin,   1801-1860. 

writer  through  the  courtesy  of  Professor  Joubin,  and  a  copy 
of  it  is  represented  in  Fig.  82.  His  picture  bespeaks  his  per- 
sonaHty.    The  quiet  refinement  and  sincerity  of  his  face  are 


266  BIOLOGY   AND    ITS    MAKERS 

evident.  Professor  Joubin  published,  in  1901  (Archives  de 
Parasitologie),  a  biographical  sketch  of  Dujardin,  with  sev- 
eral illustrations,  including  this  portrait  and  another  one 
which  is  very  interesting,  showing  him  in  academic  costume. 
Thanks  to  the  spread  of  information  of  the  kind  contained 
in  that  article,  Dujardin  is  coming  into  wider  recognition, 
and  will  occupy  the  historical  position  to  which  his  researches 
entitle  him. 

It  was  while  studying  the  protozoa  that  he  began  to  take 
particular  notice  of  the  substance  of  which  their  bodies  are 
composed;  and  in  1835  he  described  it  as  a  living  jelly 
endowed  with  all  the  qualities  of  life.  He  had  seen  the  same 
jelly-like  substance  exuding  from  the  injured  parts  of  worms, 
and  recognized  it  as  the  same  material  that  makes  the  body 
of  protozoa.  He  observed  it  very  carefully  in  the  ciliated 
infusoria — in  Paramoecium,  in  Vorticella,  and  other  forms, 
but  he  was  not  satisfied  with  mere  microscopic  observation 
of  its  structure.  He  tested  its  solubility,  he  subjected  it  to 
the  action  of  alcohol,  nitric  acid,  potash,  and  other  chemical 
substances,  and  thereby  distinguished  it  from  albumen, 
mucus,  gelatin,  etc. 

Inasmuch  as  this  substance  manifestly  was  soft,  Dujardin 
proposed  for  it  the  name  of  sarcode,  from  the  Greek,  meaning 
sojt.  Thus  we  see  that  the  substance  protoplasm  was  for 
the  first  time  brought  very  definitely  to  the  attention  of  nat- 
uralists through  the  study  of  animal  forms.  For  some  time  it 
occupied  a  position  of  isolation,  but  ultimately  became  recog- 
nized as  being  identical  with  a  similar  substance  that  occurs 
in  plants.  At  the  time  of  Dujardin's  discover}^,  sarcode  was 
supposed  to  be  peculiar  to  lower  animals ;  it  was  not  known 
that  the  same  substance  made  the  living  part  of  all  animals, 
and  it  was  owing  mainly  to  this  circumstance  that  the  full 
recognition  of  its  importance  in  nature  was  delayed. 

The  fact  remains  that  the  first  careful  studies  upon  sarcode 


THE  PHYSICAL   BASIS    OF    LIFE 


267 


were  due  to  Dujardin,  and,  therefore,  we  must  include  him 
among  the  founders  of  modem  biology. 

Purkinje. — The  observations  of  the  Bohemian  investi- 
gator Purkinje  (1787-1869)  form  a  link  in  the  chain  of  events 
leading  up  to  the  recognition  of  protoplasm.  Athough 
Purkinje  is  especially  remembered  for  other  scientific  contri- 


FiG.  83. — Purkinje,  1787-1869. 


butions,  he  was  the  first  to  make  use  of  the  name  protoplasm 
for  living  matter,  by  applying  it  to  the  formative  substance 
within  the  eggs  of  animals  and  within  the  cells  of  the  embryo. 
His  portrait  is  not  frequently  seen,  and,  therefore,  is  included 
here  (Fig.  83),  to  give  a  more  complete  series  of  pictures  of 
the  men  who  were  directly  connected  with  the  development 
of  the  protoplasm  idea.     Purkinje  was  successively  a  pro- 


268 


BIOLOGY   AND    ITS    MAKERS 


fessor  in  the  universities  of  Breslau  and  Prague.  His  ana- 
tomical laboratory  at  Breslau  is  notable  as  being  one  of  the 
earliest  (1825)  open  to  students.  He  went  to  Prague  in 
1850  as  professor  of  physiology. 

Von  Mohl. — In  1846,  eleven  years  after  the  discovery  of 
Dujardin,  the  eminent  botanist  Hugo  von  Mohl  (1805-1872) 
designated  a  particular  part  of  the  living  contents  of  the  vege- 
table cell  by  the  term  protoplasma.     The  viscid,  jelly-like 


Fig.  84. — Carl  Nageli,  181 7-1 891. 

substance  in  plants  had  in  the  mean  time  come  to  be  known 
under  the  expressive  term  of  plant  ''schleim."  He  distin- 
guished the  firmer  mucilaginous  and  granular  constituent, 
found  just  under  the  cell  membrane,  from  the  watery  cell-sap 
that  occupies  the  interior  of  the  cell.  It  was  to  the  former 
part  that  he  gave  the  name  protoplasma.     Previous  to  this, 


THE   PHYSICAL   BASIS    OF    LIFE  269 

the  botanist  Nageli  had  studied  this  living  substance,  and 
perceived  that  it  was  nitrogenous  matter.  This  was  a  dis- 
tinct step  in  advance  of  the  vague  and  indefinite  idea  of 
Schleiden,  who  had  in  reality  noticed  protoplasm  in  1838, 
but  thought  of  it  merely  as  gum.  The  highly  accom])lished 
investigator  N  ageli  (Fig.  84)  made  a  great  place  for  himself 


Fig.  85. — Hugo  von  Mohl,   1805-1872. 

in  botanical  investigation,  and  his  name  is  connected  with 
several  fundamental  ideas  of  biology.  To  Von  Mohl,  how- 
ever, belongs  the  credit  of  having  brought  the  word  proto- 
plasm into  general  use.  He  stands  in  ,the  direct  line  of 
development,  while  Purkinje,  who  first  employed  the  word 


27©  BIOLOGY   AND    ITS    MAKERS 

protoplasm,  stands  somewhat  aside,  but  his  name,  neverthe- 
less, should  be  connected  with  the  establishment  of  the 
protoplasm  doctrine. 

Von  Mohl  (Fig.  85)  was  an  important  man  in  botany. 
Early  in  life  he  showed  a  great  love  for  natural  science,  and 
as  in  his  day  medical  instruction  afforded  the  best  oppor- 
tunities for  a  man  with  scientific  tastes,  he  entered  upon  that 
course  of  study  in  Tubingen  at  the  age  of  eighteen.  He  took 
his  degree  of  doctor  of  medicine  in  1823,  and  spent  several 
years  in  Munich.  He  became  professor  of  physiology  in 
Bern  in  1832,  and  three  years  later  was  transferred  to 
Tubingen  as  professor  of  botany.  Here  he  remained  to  the 
end  of  his  life,  refusing  invitations  to  institutions  elsewhere. 
He  never  married,  and,  without  the  cares  and  joys  of  a 
family,  led  a  solitary  and  uneventful  life,  devoted  to  botan- 
ical investigation. 

Cohn. — ^After  Von  Mohl's  studies  on  "plant  schleim'^ 
there  was  a  general  movement  toward  the  conclusion  that 
the  sarcode  of  the  zoologists  and  the  protoplasm  of  the  bot- 
anists were  one  and  the  same  substance.  This  notion  was  in 
the  minds  of  more  than  one  worker,  but  it  is  perhaps  to  Fer- 
dinand Cohn  (i 828-1 898)  that  the  credit  should  be  given 
for  bringing  the  question  to  a  head.  After  a  study  of  the 
remarkable  movements  of  the  active  spores  of  one  of  the 
simplest  plants  (protococcus),  he  said  that  vegetable  proto- 
plasm and  animal  sarcode,  "if  not  identical,  must  be,  at 
any  rate,  in  the  highest  degree  analogous  substances " 
(Geddes).  • 

Cohn  (Fig.  86)  was  for  nearly  forty  years  professor  of 
botany  in  the  University  of  Breslau,  and  during  his  long  life 
as  an  investigator  greatly  advanced  the  knowledge  of  bac- 
teria. His  statement  referred  to  above  was  made  when  he 
was  twenty-two  years  of  age,  and  ran  too  far  ahead  of  the 
evidence  then  accumulated;   it  merely  anticipated  the  com- 


THE  PHYSICAL   BASIS  OF    LIFE 


271 


ing  period  of  the  acceptance  of  the  conclusion  in  its  full 
significance. 

De  Bary. — We  find,  then,  in  the  middle  years  of  the 
nineteenth  century  the  idea  launched  that  sarcode  and  pro- 
toplasm are  identical,  but  it  was  not  yet  definitely  established 


Fig.  86. — Ferdinand  Cohn,   1828-1898. 


that  the  sarcode  of  lower  animals  is  the  same  as  the  living 
substance  of  the  higher  ones,  and  there  was,  therefore,  lacking 
an  essential  factor  to  the  conclusion  that  there  is  only  one 
general  form  of  living  matter  in  all  organisms.  It  took 
another  ten  years  of  investigation  to  reach  this  end. 

The  most  important  contributions  from  the  botanical  side 
during  this  period  were  the  splendid  researches  of  De  Bar}^ 
(Fig.  87)  on  the  myxomycetes,  published  in  1859.  Here  the 
resemblance  between  sarcode  and  protoplasm  was  brought  out 


272 


BIOLOGY    AND    ITS    MAKERS 


with  great  clearness.  The  myxomycetes  are,  in  one  condition, 
masses  of  vegetable  protoplasm,  the  movements  and  other 
characieristics  of  which  were  shown  to  resemble  strongly 
those  of  the  protozoa.  DeBary's  great  fame  as  a  botanist 
has  made  his  name  widely  known. 

In  1858  Virchow  also,  by  his  extensive  studies  in  the 
pathology  of  living  cells,  added  one  more  link  to  the  chain 


Fig.  87. — Heinrich  A.  de  Bary,  1831-1888. 


that  was  soon  to  be  recognized  as  encircling  the  new  domain 
of  modern  biology. 

Schultze. — ^As  the  culmination  of  a  long  period  of  work, 
Max  Schultze,  in  t86t.  placed  the  conception  of  the  identity 


THE    PHYSICAL    BASIS    OF  LIFE 


273 


between  animal  sarcode  and  vegetable  protoplasm  upon  an 
unassailable  basis,  and  therefore  he  has  received  the  title  of 


Fig.  88. — Max  Schultze,   1825-1874. 

"the  father  of  modern  biology."  He  showed  that  sarcode, 
which  was  supposed  to  be  confined  to  the  lower  invertebrates, 
is  also  present  in  the  tissues  of  higher  animals,  and  there  ex- 

iS 


274  BIOLOGY   AND    ITS    MAKERS 

hibits  the  same  properties.  The  quahties  of  contractility  and 
irritability  were  especially  indicated.  It  was  on  physiological 
likeness,  rather  than  on  structural  grounds,  that  he  formed 
his  sweeping  conclusions.  He  showed  also  that  sarcode 
agreed  in  physiological  properties  with  protoplasm  in  plants, 
and  that  the  two  living  substances  were  practically  identical. 
His  paper  of  1861  considers  the  living  substance  in  muscles 
(Ueber  Muskelkorperchen  und  das  was  man  eine  Zelle  zu 
nennen  habe),  but  in  this  he  had  been  partly  anticipated  by 
Ecker  who,  in  1849,  compared  the  ''formed  contractile  sub- 
stance" of  muscles  with  the  "  unformed  contractile  substance'* 
of  the  lower  types  of  animal  life  (Geddes). 

The  clear-cut,  intellectual  face  of  Schultze  (Fig.  88)  is 
that  of  an  admirable  man  with  a  combination  of  the  artistic 
and  the  scientific  temperaments.  He  was  greatly  interested 
in  music  from  his  youth  up,  and  by  the  side  of  his  microscope 
was  his  well-beloved  violin.  He  was  some  time  professor  in 
the  University  of  Halle,  and  in  1859  went  to  Bonn  as  pro- 
fessor of  anatomy  and  director  of  the  Anatomical  Institute. 
His  service  to  histology  has  already  been  spoken  of  (Chapter 
VIII). 

This  astute  observer  will  have  an  enduring  fame  in 
biological  science,  not  only  for  the  part  he  played  in  the 
development  of  the  protoplasm  idea,  but  also  on  account  of 
other  extensive  labors.  In  1866  he  founded  the  leading 
periodical  in  microscopic  anatomy,  the  Archiv  jiir  Mikro- 
scopische  Anatomie.  This  periodical  was  continued  after 
the  untimely  death  of  Schultze  in  1874,  and  to-day  is  one  of 
the  leading  biological  periodicals. 

It  is  easy,  looking  backward,  to  observe  that  the  period 
between  1840  and  i860  was  a  very  important  one  for  modem 
biology.  Many  new  ideas  were  coming  into  existence,  but 
through  this  period  we  can  trace  distinctly,  step  by  step,  the 
gradual  approach  to  the  idea  that  protoplasm,  the  living 


THE   PHYSICAL   BASIS    OF    LIFE  275 

substance  of  organism,  is  practically  the  same  in  plants  and 
in  animals.  Let  us  picture  to  ourselves  the  consequences  of 
the  acceptance  of  this  idea.  Now  for  the  first  time  physiol- 
ogists began  to  have  their  attention  directed  to  the  actually 
living  substance;  now  for  the  first  time  they  saw  clearly 
that  all  future  progress  was  to  be  made  by  studying  this  living 
substance — the  seat  of  vital  activity.  This  was  the  beginning 
of  modern  biology. 

Protoplasm  is  the  particular  object  of  study  for  the  biol- 
ogist. To  observe  its  properties,  to  determine  how  it  be- 
haves under  different  conditions,  how  it  responds  to  stimuli 
and  natural  agencies,  to  discover  the  relation  of  the  internal 
changes  to  the  outside  agencies :  these,  which  constitute  the 
fundamental  ideas  of  biology,  were  for  the  first  time  brought 
directly  to  the  attention  of  the  naturalist,  about  the  year 
i860 — that  epoch-making  time  when  appeared  Darwin's 
Origin  oj  Species  and  Spencer's  First  Principles, 


CHAPTER  XIII 

THE  WORK  OF  PASTEUR,   KOCH,   AND  OTHERS 

The  knowledge  of  bacteria,  those  minutest  forms  of  life, 
has  exerted  a  profound  influence  upon  the  development  of 
general  biology.  There  are  many  questions  relating  to  bac- 
teria that  are  strictly  medical,  but  other  phases  of  their  life 
and  activities  are  broadly  biological,  and  some  of  those 
broader  aspects  will  next  be  brought  under  consideration. 

The  bacteria  were  first  described  by  I^eeuwenhoek  in 
1687,  twelve  years  after  his  discovery  of  the  microscopic 
animalcula  now  called  protozoa.  They  are  so  infinitesimal 
in  size  that  under  his  microscope  they  appeared  as  mere 
specks,  and,  naturally,  observation  of  these  minute  organ- 
isms was  suspended  until  nearly  the  middle  of  the  nineteenth 
century,  after  the  improvement  of  microscope  lenses.  It  is 
characteristic  of  the  little  knowledge  of  bacteria  in  Linnaeus's 
period  that  he  grouped  them  into  an  order,  with  other  micro- 
scopic forms,  under  the  name  chaos. 

At  first  sight,  the  bacteria  appear  too  minute  to  figure 
largely  in  human  affairs,  but  a  great  department  of  natural 
science — bacteriology— has  been  opened  by  the  study  of  their 
activities,  and  it  must  be  admitted  that  the  development  of 
the  science  of  bacteriology  has  been  of  great  practical  im- 
portance. The  knowledge  derived  from  experimental  studies 
of  the  bacteria  has  been  the  chief  source  of  light  in  an  obscure 
domain  which  profoundly  affects  the  well-being  of  mankind. 
To  the  advance  of  such  knowledge  we  owe  the  germ-theory 
of  disease  and  the  ability  of  medical  men  to  cope  with  con- 

276 


PASTEUR,    KOCH,  AND    OTHERS  277 

tagious  diseases.  The  three  greatest  names  connected  with 
the  rise  of  bacteriology  are  those  of  Pasteur,  Koch,  and  Lister, 
the  resuks  of  whose  labors  will  be  considered  later. 

Among  the  general  topics  which  have  been  clustered 
around  the  study  of  bacteria  we  take  up,  first,  the  question 
of  the  spontaneous  origin  of  life. 

The  Spontaneous  Origin  of  Life 

It  will  be  readily  understood  that  the  question  of  the  spon- 
taneous generation  of  life  is  a  fundamental  one  for  the  biol- 
ogist. Does  life  always  arise  from  previously  existing  life, 
or  under  certain  conditions  is  it  developed  spontaneously? 
Is  there,  in  the  inorganic  world,  a  happy  concourse  of  atoms 
that  beconie  chained  together  through  the  action  of  the  sun's 
rays  and  other  natural  forces,  so  that  a  molecule  of  living 
matter  is  constructed  in  nature's  laboratory  without  contact 
or  close  association  with  living  substance?  This  is  a  ques- 
tion of  biogenesis — life  from  previous  life — or  of  abiogenesis 
— life  without  preexisting  life  or  from  inorganic  matter  alone. 

It  is  a  question  with  a  long  histor}^  Its  earliest  phases  do 
not  involve  any  consideration  of  microscopic  forms,  since  they 
were  unknown,  but  its  middle  and  its  modern  aspect  are  con- 
cerned especially  with  bacteria  and  other  microscopic  organ- 
isms. The  historical  development  of  the  problem  may  be 
conveniently  considered  under  three  divisions :  I.  The  period 
from  Aristotle,  325  B.C.,  to  the  experiments  of  Redi,  in  1668; 
II.  From  the  experiments  of  Redi  to  those  of  Schulze  and 
Schwann  in  1836  and  1837;  III.  The  modern  phase,  ex- 
tending from  Pouch et's  observations  in  1859  to  the  present. 

I.  From  Aristotle  to  Redi. — During  the  first  period,  the 
notion  of  spontaneous  generation  was  universally  accepted, 
and  the  whole  question  of  spontaneous  origin  of  life  was  in 
a  crude  and  grotesque  condition.     It  was  thought  that  frogs 


278  BIOLOGY   AND   ITS   MAKERS 

and  toads  and  other  animals  arose  from  the  mud  of  ponds 
and  streams  through  the  vivifying  action  of  the  sun's  rays. 
Rats  were  supposed  to  come  from  the  river  Nile,  the  dew  was 
supposed  to  give  origin  to  insects,  etc. 

The  scientific  writers  of  this  period  had  little  openness  of 
mind,  and  they  indulged  in  scornful  and  sarcastic  comments 
at  the  expense  of  those  who  doubted  the  occurrence  of 
spontaneous  generation.  In  the  seventeenth  century  Alex- 
ander Ross,  commenting  on  Sir  Thomas  Brown's  doubt  as 
to  whether  mice  may  be  bred  by  putrefaction,  flays  his  an- 
tagonist in  the  following  words:  "So  may  we  doubt  whether 
in  cheese  and  timber  worms  are  generated,  or  if  beetles  and 
wasps  in  cow-dung,  or  if  butterflies,  locusts,  shell-fish,  snails, 
eels,  and  such  life  be  procreated  of  putrefied  matter,  which 
is  to  receive  the  form  of  that  creature  to  which  it  is  by 
formative  power  disposed.  To  question  this  is  to  question 
reason,  sense,  and  experience.  If  he  doubts  this,  let  him  go 
to  Egypt,  and  there  he  will  find  the  fields  swarming  with 
mice  begot  of  the  mud  of  Nylus,  to  the  great  calamity  of 
the  inhabitants." 

II.  From  Redi  to  Schwann. — ^The  second  period  em- 
braces the  experimental  tests  of  Redi  (1668),  Spallanzani 
(1775),  and  Schwann  (1837) — ^notable  achievements  that 
resulted  in  a  verdict  for  the  adherents  to  the  doctrine  of 
biogenesis.  Here  the  question  might  have  rested  had  it 
not  been  opened  upon  theoretical  ground  by  Pouchet  in 
1859. 

The  First  Experiments. — The  belief  in  spontaneous  gen- 
eration, which  was  so  firmly  implanted  in  the  minds  of  natu- 
ralists, was  subjected  to  an  experimental  test  in  1668  by  the 
Italian  Redi.  It  is  a  curious  circumstance,  but  one  that 
throws  great  light  upon  the  condition  of  intellectual  develop- 
ment of  the  period,  that  no  one  previous  to  Redi  had  at- 
tempted to  test  the  truth  or  falsity  of  the  theory  of  spon- 


PASTEUR,   KOCH,  AND  OTHERS  279 

taneous  generation.     To  approach  this  question  from  the 
experimental  side  was  to  do  a  great  service  to  science. 

The  experiments  of  Redi  were  simple  and  homely.  He 
exposed  meat  in  wide-mouthed  flasks,  some  of  which  were  left 
uncovered,  some  covered  with  paper,  and  others  with  a  fine 
Neapolitan  veil.  The  meat  in  all  these  vessels  became 
spoiled,  and  flies,  being  attracted  by  the  smell  of  decaying 
mieat,  laid  eggs  in  that  which  was  exposed,  and  there  came 
from  it  a  large  crop  of  maggots.  The  meat  in  the  covered 
ilasks  also  decayed  in  a  similar  manner,  without  the  appear- 
ance of  maggots  within  it;  and  in  those  vessels  covered  by 
veiling  the  flies  laid  their  eggs  upon  the  netting.  There  they 
hatched,  and  the  maggots,  instead  of  appearing  in  the  meat, 
appeared  on  the  surface  of  the  covering.  From  this  Redi  con- 
cluded that  maggots  arise  in  decaying  meat  from  the  hatching 
of  the  eggs  of  insects,  but  inasmuch  as  these  animals  had  been 
supposed  to  arise  spontaneously  within  the  decaying  meat,  the 
experiment  took  the  ground  from  under  that  hypothesis. 

He  made  other  observations  on  the  generation  of  insects, 
but  with  acute  scientific  analysis  never  allowed  his  conclusions 
to  run  ahead  of  his  observations.  He  suggested,  however, 
the  probability  that  all  cases  of  the  supposed  production  of  life 
from  dead  matter  were  due  to  the  introduction  of  living  germs 
from  without.  The  good  work  begun  by  Redi  was  confirmed 
and  extended  by  Swammerdam  (1637-1681)  and  Vallisnieri 
(1661-1730),  until  the  notion  of  the  spontaneous  origin  of  any 
forms  of  life  visible  to  the  unaided  eye  was  banished  from 
the  minds  of  scientific  men. 

Redi  (Fig.  89)  was  an  Italian  physician  living  in  Arentino, 
distinguished  alike  for  his  attainments  in  literature  and  for 
his  achievements  in  natural  science.  He  was  medical  adviser 
to  two  of  the  grand  dukes  of  Tuscany,  and  a  member  of  the 
Academy  of  Crusca.  Poetry  as  well  as  other  literary  com- 
positions shared  his  time  with  scientific  occupations.     His 


28o 


BIOLOGY   AND    ITS    MAKERS 


collected  works,  literary,  scientific,  and  medical,  were  pub- 
lished in  nine  octavo  volumes  in  Milan,  1809-1811.  This 
collection  includes  his  life  and  letters,  and   embraces  one 


Fig.  89. — Francesco  Redi,   1626-1697. 

volume  of  sonnets.  The  book  that  has  been  referred  to  as 
containing  his  experiments  was  entitled  Esperienze  Intorno 
Alia  Generazione  DegPInsetti,  and  first  saw  the  light  in 
quarto  form  in  Florence  in  1668.  It  went  through  five 
editions  in  twenty  years.     Some  of  the  volumes  were  trans- 


PASTEUR,    KOCH,    AND    OTHERS  281 

lated  into  Latin,  and  were  published  in  miniature,  making 
books  not  more  than  four  inches  high.  Huxley  says:  "The 
extreme  simplicity  of  his  experiments,  and  the  clearness  of 
his  arguments,  gained  for  his  views  and  for  their  conse- 
quences almost  universal  acceptance." 

New  Form  of  the  Question.— The  question  of  the  spon- 
taneous generation  of  life  was  soon  to  take  on  a  new  aspect. 
Seven  years  after  the  experiments  of  Redi,  Leeuwenhoek 
made  known  a  new  world  of  microscopic  organisms — the 
infusoria — and,  as  we  have  seen,  he  discovered,  in  1687,  those 
still  minuter  forms,  the  bacteria.  Strictly  speaking,  the 
bacteria,  on  account  of  their  extreme  minuteness,  were  lost 
sight  of,  but  spontaneous  generation  was  evoked  to  account 
for  the  birth  of  all  microscopic  organisms,  and  the  question 
circled  mainly  around  the  infusorial  animalcula.  While  the 
belief  in  the  spontaneous  generation  of  life  among  forms 
visible  to  the  unaided  eye  had  been  surrendered,  nevertheless 
doubts  were  entertained  as  to  the  origin  of  microscopic  organ- 
isms, and  it  was  now  asserted  that  here  were  found  the  be- 
ginnings of  life — the  place  where  inorganic  material  was 
changed  through  natural  agencies  into  organized  beings 
microscopic  in  size. 

More  than  seventy  years  elapsed  before  the  matter  was 
again  subjected  to  experimental  tests.  Then  Needham, 
using  the  method  of  Redi,  began  to  experiment  on  the  pro- 
duction of  microscopic  animalcula.  In  many  of  his  experi- 
ments he  was  associated  with  Buffon,  the  great  French  nat- 
uralist, who  had  a  theory  of  organic  molecules  that  he  wished 
to  sustain.  Needham  (1713-1784),  a  priest  of  the  Catholic 
faith,  was  an  Englishman  living  on  the  Continent ;  he  was 
for  many  years  director  of  the  Academy  of  Maria  Theresa  at 
Brussels.  He  engaged  in  scientific  investigations  in  connec- 
tion with  his  work  of  teaching.  The  results  of  Needham's 
first  experiments  were  published  in  1 748.     These  experiments 


282  BIOLOGY   AND    ITS    MAKERS 

were  conducted  by  extracting  the  juices  of  meat  by  boiling; 
by  then  enclosing  the  juices  in  vials,  the  latter  being  carefully 
corked  and  sealed  with  mastic;  by  subjecting  the  sealed 
bottles,  finally,  to  heat,  and  setting  them  away  to  cool.  In 
due  course  of  time,  the  fluids  thus  treated  became  infected 
with  microscopic  life,  and,  inasmuch  as  Ncedham  believed 
that  he  had  killed  all  living  germis  by  repeated  heating,  he 
concluded  that  the  living  forms  had  been  produced  by  spon- 
taneous generation. 

Spallanzani. — The  epoch-making  researches  of  Spallan- 
zani,  a  fellow-countryman  of  Redi,  were  needed  to  point  out 
the  error  in  Needham's  conclusions.  Spallanzani  (Fig.  90) 
was  one  of  the  most  eminent  men  of  his  time.  He  was 
educated  for  the  church,  and,  therefore,  he  is  usually  known 
under  the  title  of  Abbe  Spallanzani.  He  did  not,  however, 
actively  engage  in  his  churchly  offices,  but,  following  an  innate 
love  of  natural  science  and  of  investigation,  devoted  himself 
to  experiments  and  researches  and  to  teaching.  He  was  first 
a  professor  at  Bologna,  and  afterward  at  the  University  of 
Pavia.  He  made  many  additions  to  knowledge  of  the 
development  and  the  physiology  of  organisms,  and  he  was 
the  first  to  make  use  of  glass  flasks  in  the  experimental  study 
of  the  question  of  the  spontaneous  generation  of  life. 

Spallanzani  thought  that  the  experiments  of  Needham 
had  not  been  conducted  with  sufficient  care  and  precision; 
accordingly,  he  made  use  of  glass  flasks  with  slender  necks 
which  could  be  hermetically  sealed  after  the  nutrient  fluids 
had  been  introduced.  The  vials  which  Needham  used  as 
containers  were  simply  corked  and  sealed  with  mastic,  and 
it  was  by  no  means  certain  that  the  entrance  of  air  after 
heating  had  been  prevented;  moreover,  no  record  was  made 
by  Needham  of  the  temperature  and  the  time  of  heating  to 
which  his  bottles  and  fluids  had  been  subjected. 

Spallanzani  took  nutrient  fluids,  such  as  the  juices  of  vege- 


PASTEUR,    KOCH,    AND    OTHERS 


283 


tables  and  meats  which  had  been  extracted  by  boiling,  placed 
them  in  clean  flasks,  the  necks  of  which  were  hermetically 
sealed  in  flame,  and  afterward  immersed  them  in  boiling 
water  for  three-quarters  of  an  hour,  in  order  to  destroy  all 


Fig.  90. — Lazzaro  Spallanzani,   i 729-1 799. 


germs  that  might  be  contained  in  them.  The  organic  infu- 
sions of  Spallanzani  remained  free  from  change.  It  was 
then,  as  now,  a  well-known  fact  that  organic  fluids,  when 
exposed  to  air,  quickly  decompose  and  acquire  a  bad  smell; 


284  BIOLOGY   AND    ITS    MAKERS 

they  soon  become  turbid,  and  in  a  little  time  a  scum  is 
formed  upon  their  surface.  The  fluids  in  the  flasks  of 
Spallanzani  remained  of  the  same  appearance  and  consistency 
as  when  they  were  first  introduced  into  the  vessel,  and  the 
obvious  conclusion  was  drawn  that  microscopic  life  is  not 
spontaneously  formed  within  nutrient  fluids. 

"But  Needham  was  not  satisfied  with  these  results,  and 
with  a  show  of  reason  maintained  that  such  a  prolonged 
boiling  would  destroy  not  only  germs,  but  the  germinative, 
or,  as  he  called  it,  the  'vegetative  force'  of  the  infusion 
itself.  Spallanzani  easily  disposed  of  this  objection  by  show- 
ing that  when  the  infusions  were  again  exposed  to  the  air, 
no  matter  how  severe  or  prolonged  the  boiling  to  which  they 
had  been  subjected,  the  infusoria  reappeared.  His  experi- 
ments were  made  in  great  numbers,  with  different  infusions, 
and  were  conducted  with  the  utmost  care  and  precision" 
(Dunster).  It  must  be  confessed,  however,  that  the  success 
of  his  experiments  was  owing  largely  to  the  purity  of  the  air 
in  which  he  v;orked,  the  more  resistant  atmospheric  germs 
were  not  present:  as  Wyman  showed,  long  afterward,  that 
germs  may  retain  their  vitality  after  being  subjected  for 
several  hours  to  the  temperature  of  boiling  water. 

Schulze  and  Schwann. — ^The  results  of  Spallanzani's  ex- 
periments were  published  in  1775,  and  were  generally  re- 
garded by  the  naturalists  of  that  period  as  answering  in  the 
negative  the  question  of  the  spontaneous  generation  of  life. 
Doubts  began  to  arise  as  to  the  conclusive  nature  of  Spal- 
lanzani's experiments,  on  account  of  the  discoveiy  of  the  part 
which  oxygen  plays  in  reference  to  life.  The  discovery  of 
oxygen,  one  of  the  greatest  scientific  events  of  the  eighteenth 
century,  was  made  by  Priestley  in  1774.  It  was  soon  shown 
that  oxygen  is  necessar}^  to  all  forms  of  life,  and  the  question 
was  raised :  Had  not  the  boiling  of  the  closed  flasks  changed 
the  oxygen  so  that  through  the  heating  process  it  had  lost  its 


PASTEUR,    KOCH,    AND    OTHERS  285 

life-giving  properties?  This  doubt  grew  until  a  reexamina- 
tion of  the  question  of  spontaneous  generation  became  nec- 
essary under  conditions  in  which  the  nutrient  fluids  were 
made  accessible  to  the  outside  air. 

In  1836  Franz  Schulze,  and,  in  the  following  year, 
Theodor  Schwann,  devised  experiments  to  test  the  question 
on  this  new  basis.  Schwann  is  known  to  us  as  the  founder  of 
the  cell-theory,  but  we  must  not  confuse  Schulze  with  Max 
Schultze,  who  established  the  protoplasm  doctrine.  In  the 
experiments  of  Schulze,  a  flask  was  arranged  containing 
nutrient  fluids,  with  a  large  cork  perforated  and  closely  fitted 
with  bent  glass  tubes  connected  on  one  side  with  a  series  of 
bulbs  in  which  were  placed  sulphuric  acid  and  other  chemical 
substances.  An  aspirator  was  attached  to  the  other  end  of 
this  system,  and  air  from  the  outside  was  sucked  into  the 
flask,  passing  on  its  way  through  the  bulbs  containing  the 
chemical  substances.  The  purpose  of  this  was  to  remove 
the  floating  germs  that  exist  in  the  air,  while  the  air  itself 
was  shown,  through  other  experiments  by  Schwann,  to  re- 
main unchanged. 

Tyndall  says  in  reference  to  these  experiments:  **Here 
again  the  success  of  Schulze  was  due  to  his  working  in 
comparatively  pure  air,  but  even  in  such  air  his  experiment 
is  a  risky  one.  Germs  will  pass  unwetted  and  unscathed 
through  sulphuric  acid  unless  the  most  special  care  is  taken 
to  detain  them.  I  have  repeatedly  failed,  by  repeating 
Schulze's  experiments,  to  obtain  his  results.  Others  have 
failed  likewise.  The  air  passes  in  bubbles  through  the 
bulbs,  and  to  render  the  method  secure,  the  passage  of  the 
air  must  be  so  slow  as  to  cause  the  whole  of  its  floating 
matter,  even  to  the  very  core  of  each  bubble,  to  touch  the 
surrounding  fluid.  But  if  this  precaution  be  observed  water 
■will  he  found  quite  as  effectual  as  sulphuric  acid.^^ 

Schwann's  apparatus  was  similar  in  construction,  except 


286  BIOLOGY    AND    ITS    MAKERS 

that  the  bent  tube  on  one  side  was  surrounded  by  a  jacket 
of  metal  and  was  subjected  to  a  very  high  temperature  while 
the  air  was  being  drawn  through  it,  the  effect  being  to  kill 
any  floating  germs  that  might  exist  in  the  air.  Great  care 
was  taken  by  both  experimenters  to  have  their  flasks  and  fluids 
thoroughly  sterilized,  and  the  results  of  their  experiments  were 
to  show  that  the  nutrient  fluids  remained  uncontaminated. 

These  experiments  proved  that  there  is  something  in 
the  atmosphere  which,  unless  it  be  removed  or  rendered 
inactive,  produces  life  within  nutrient  fluids,  but  whether 
this  something  is  solid,  fluid,  or  gaseous  did  not  appear 
from  the  experiments.  It  remained  for  Helmholtz  to  show, 
as  he  did  in  1843,  ^^^^  ^his  something  will  not  pass  through 
a  moist  animal  membrane,  and  is  therefore  a  solid.  The 
results  so  far  reached  satisfied  the  minds  of  scientific  men, 
and  the  question  of  the  spontaneous  origin  of  life  was. 
regarded  as  having  been  finally  set  at  rest. 

III.  The  Third  Period.  Pouchet. — We  come  now  to  con- 
sider the  third  historical  phase  of  this  question.  Although  it 
had  apparently  been  set  at  rest,  the  question  was  unexpect- 
edly opened  again  in  1859  by  the  Frenchman  Pouchet,  the 
director  of  the  Natural  History  Aluseum  of  Rouen.  The 
frame  of  mind  which  Pouchet  brought  to  his  experimental 
investigations  was  fatal  to  unbiased  conclusions:  ''When, 
by  meditation,''''  he  says,  in  the  opening  paragraph  of  his  book 
on  Hetero genesis,  ''it  was  evident  to  me  that  spontaneous 
generation  was  one  of  the  means  employed  by  nature  for  the 
production  of  living  beings,  I  applied  myself  to  discover  by 
what  means  one  could  place  these  phenomena  in  evidence." 
Although  he  experimented,  his  case  was  prejudiced  by 
metaphysical  considerations.  He  repeated  the  experiments 
of  previous  observers  with  opposite  results,  and  therefore  he 
declared  his  belief  in  the  falsity  of  the  conclusions  of  Spal- 
lanzani,  Schulze,  and  Schwann. 


PASTEUR,    KOCH,    AND    OTHERS  287 

He  planned  and  executed  one  experiment  which  he  sup- 
posed was  conclusive.  In  introducing  it  he  said:  "The 
opponents  of  spontaneous  generation  assert  that  the  germs  of 
microscopic  organisms  exist  in  the  air,  which  transports  them 
to  a  distance.  What,  then,  will  these  opponents  say  if  I 
succeed  in  introducing  the  generation  of  living  organisms, 
while  substituting  artificial  air  for  that  of  the  atmosphere?" 

He  filled  a  flask  with  boiling  water  and  sealed  it  with  great 
care.  This  he  inverted  over  a  bath  of  mercury,  thrusting 
the  neck  of  the  bottle  into  the  mercury.  When  the  water 
was  cooled,  he  opened  the  neck  of  the  bottle,  still  under  the 
mercury,  and  connected  it  with  a  chemical  retort  containing 
the  constituents  for  the  liberation  of  oxygen.  By  heating 
the  retort,  oxygen  was  driven  off  from  the  chemical  salts 
contained  in  it,  and  being  a  gas,  the  oxygen  passed  through 
the  connecting  tube  and  bubbled  up  through  the  water  of 
the  bottle,  accumulating  at  the  upper  surface,  and  by  pressure 
forcing  water  out  of  the  bottle.  After  the  bottle  was  about 
half  filled  with  oxygen  imprisoned  above  the  water,  Pouchet 
took  a  pinch  of  hay  that  had  been  heated  to  a  high  tempera- 
ture in  an  oven,  and  with  a  pair  of  sterilized  forceps  pushed 
it  underneath  the  mercury  and  into  the  mouth  of  the  bottle, 
where  the  hay  floated  into  the  water  and  distributed  itself. 

He  thus  produced  a  hay  infusion  in  contact  with  pure  oxy- 
gen, and  after  a  few  days  this  hay  infusion  was  seen  to  be  cloudy 
and  turbid.  It  was,  in  fact,  swarming  with  micro-organisms. 
Pouchet  pointed  with  triumphant  spirit  to  the  apparently 
rigorous  way  in  which  his  experiment  had  been  carried  on: 
''Where,"  said  he,  ''does  this  life  come  from?  It  can  not 
come  from  the  water  which  had  been  boiled,  destroying  all 
living  germs  that  may  have  existed  in  it.  It  can  not  come 
from  the  oxygen  which  was  produced  at  the  temperature 
of  incandescence.  It  can  not  have  been  carried  in  the  hay, 
which  had  been  heated  for  a  long  period  before  being  intro- 


288  BIOLOGY   AND    ITS    MAKERS 

duced  into  the  water."     He  declared  that  this  life  was,  there- 
fore, of  spontaneous  origin. 

The  controversy  now  revived,  and  waxed  warm  under  the 
insistence  of  Pouchet  and  his  adherents.  Finally  the  Acad- 
emy of  Sciences,  in  the  hope  of  bringing  it  to  a  conclusion, 
appointed  a  committee  to  decide  upon  conflicting  claims. 

Pasteur. — Pasteur  had  entered  into  the  investigation  of 
the  subject  about  i860,  and,  with  wonderful  skill  and  acumen, 
was  removing  all  possible  grounds  for  the  conclusions  of 
Pouchet  and  his  followers.  In  1864,  before  a  brilliant 
audience  at  the  Sorbonne,  he  repeated  the  experiment  out- 
lined above  and  showed  the  source  of  error.  In  a  darkened 
room  he  directed  a  bright  beam  of  light  upon  the  apparatus, 
and  his  auditors  could  see  in  the  intense  illumination  that 
the  surface  of  the  mercury  was  covered  with  dust  particles. 
Pasteur  then  showed  that  when  a  body  was  plunged  beneath 
the  mercury,  some  of  these  surface  granules  were  carried 
with  it.  In  this  striking  manner  Pasteur  demonstrated 
that  particles  from  the  outside  had  been  introduced  into  the 
bottle  of  w^ater  by  Pouchet.  This,  however,  is  probably  not 
the  only  source  of  the  organisms  which  were  developed  in 
Pouchet's  infusions.  It  is  now  known  that  a  hay  infusion 
is  very  difficult  to  sterilize  by  heat,  and  it  is  altogether  likely 
that  the  infusions  used  by^  Pouchet  were  not  completely 
sterilized. 

The  investigation  of  the  question  requires  more  critical 
methods  than  was  at  first  supposed,  and  more  factors  enter 
into  its  solution  than  were  realized  by  Spallanzani  and 
Schwann. 

Pasteur  demonstrated  that  the  floating  particles  of  the  air 
contained  living  germs,  by  catching  them  in  the  meshes  of 
gun  cotton,  and  then  dissolving  the  cotton  with  ether  and 
examining  the  residue.  He  also  showed  that  sterilized 
organic  fluids  could  be  protected  by  a  plug  of  cotton  suffi- 


PASTEUR,    KOCH,    AND    OTHERS  289 

ciently  porous  to  admit  of  exchange  of  air,  but  matted  closely 
enough  to  entangle  the  floating  particles.  He  showed  also 
that  many  of  the  minute  organisms  do  not  require  free  oxygen 
for  their  life  processes,  but  are  able  to  take  the  oxygen  by 
chemical  decomposition  which  they  themselves  produce  from 
the  nutrient  fluids. 

Jeffries  Wyman,  of  Harvard  College,  demonstrated  that 
some  germs  are  so  resistant  to  heat  that  they  retain  their 
vitality  after  several  hours  of  boiling.  This  fact  probably 
accounts  for  the  difference  in  the  results  that  have  been 
obtained  by  experimenters.  The  germs  in  a  resting-stage 
are  surrounded  by  a  thick  protective  coat  of  cellulose, 
which  becomes  softened  and  broken  when  they  germinate. 
On  this  account  more  recent  experimenters  have  adopted  a 
method  of  discontinuous  heating  of  the  nutrient  fluid  that  is 
being  tested.  The  fluids  are  boiled  at  intervals,  so  that  the 
unusually  resistant  germs  are  killed  after  the  coating  has  been 
rendered  soft,  and  when  they  are  about  to  germinate. 

After  the  brilliant  researches  of  Pasteur,  the  question  of 
spontaneous  germination  was  once  again  regarded  as  having 
been  answered  in  the  negative;  and  so  it  is  regarded  to-day 
by  the  scientific  world.  Nevertheless,  attempts  have  been 
made  from  time  to  time,  as  by  Bastian,  of  England,  in  1872, 
to  revive  it  on  the  old  lines. 

Tyndall. — John  Tyndall  (1820-1893),  the  distinguished 
physicist,  of  London,  published,  in  1876,  the  results  of  his  ex- 
periments on  this  question,  which,  for  clearness  and  ingenuity, 
have  never  been  surpassed.  For  some  time  he  had  been 
experimenting  in  the  domain  of  physics  with  what  he  called 
optically  pure  air.  It  was  necessary  for  him  to  have  air  from 
which  the  floating  particles  had  been  sifted,  and  it  occurred 
to  him  that  he  might  expose  nutrient  fluids  to  this  optically 
pure  air,  and  thus  very  nicely  test  ,the  question  of  the 
spontaneous  origin  of  life  within  them. 
19 


290 


BIOLOGY   AND    ITS    MAKERS 


He  devised  a  box,  or  chamber,  as  shown  in  Fig.  91, 
having  in  front  a  large  glass  window,  two  small  glass  win- 
dows on  the  ends,  and  in  the  back  a  little  air-tight  trap-door. 
Through  the  bottom  of  this  box  he  had  fitted  ordinary  test 


Fig. 


91 


-Apparatus  of  Tyndall  for  Experimenting  on  Spontaneous 
Generation, 


tubes  of  the  chemist,  with  an  air-tight  surrounding,  and  on 
the  top  he  had  inserted  some  coiled  glass  tubes,  which  were 
open  at  both  ends  and  allowed  the  passage  of  air  in  and  out 
of  the  box  through  the  tortuous  passage.  In  the  middle 
of  the  top  of  the  box  was  a  round  piece  of  rubber.  When 
he  perforated  this  with  a  pinhole  the  elasticity  of  the  rub- 


PASTEUR,    KOCH,    AND    OTHERS  291 

ber  would  close  the  hole  again,  but  it  would  also  admit  of 
the  passage  through  it  of  a  small  glass  tube,  such  as  is 
called  by  chemists  a  "thistle  tube."  The  interior  of  this 
box  w^as  painted  with  a  sticky  substance  like  glycerin, 
in  order  to  retain  the  floating  particles  of  the  air  when  they 
had  once  settled  upon  its  sides  and  bottom.  The  apparatus 
having  been  prepared  in  this  way,  was  allowed  to  stand,  and 
the  floating  particles  settled  by  their  own  weight  upon 
the  bottom  and  sides  of  the  box,  so  that  day  by  day  the 
number  of  floating  particles  became  reduced,  and  finally  all 
of  them  came  to  rest. 

The  air  now  diff"ered  from  the  outside  air  in  having  been 
purified  of  all  of  its  floating  particles.  In  order  to  test  the 
complete  disappearance  of  all  particles.  Tyndall  threw  a 
beam  of  light  into  the  air  chamber.  He  kept  his  eye  in  the 
darkness  for  some  time  in  order  to  increase  its  sensitiveness ; 
then,  looking  from  the  front  through  the  glass  into  the  box, 
he  was  able  to  see  any  particles  that  might  be  floating  there. 
The  floating  particles  would  be  brightly  illuminated  by  the 
condensed  light  that  he  directed  into  the  chamber,  and 
would  become  visible.  When  there  was  complete  darkness 
within  the  chamber,  the  course  of  the  beam  of  light  was 
apparent  in  the  room  as  it  came  up  to  the  box  and  as 
it  left  the  box,  being  seen  on  account  of  the  reflection  from 
the  floating  particles  in  the  air,  but  it  could  not  be  seen 
at  all  within  the  box.  When  this  condition  was  reached, 
Tyndall  had  what  he  called  optically  pure  air,  and  he  was 
now  ready  to  introduce  the  nutrient  fluids  into  his  test  tubes. 
Through  a  thistle  tube,  thrust  into  the  rubber  diaphragm 
above,  he  was  able  to  bring  the  mouth  of  the  tube  successively 
over  the  different  test  tubes,  and,  by  pouring  different  kinds 
of  fluids  from  above,  he  was  able  to  introduce  these  into 
dift'erent  test  tubes.  These  fluids  consisted  of  mutton  broth, 
cf  turnip  broth,  and  other  decoctions  of  animal  and  vegeta- 


292  BIOLOGY   AND    ITS   MAKERS 

ble  matter.  It  is  to  be  noted  that  the  test  tubes  were  not 
corked  and  consequently  that  the  fluids  contained  within 
them  were  freely  exposed  to  the  optically  pure  air  within  the 
chamber. 

The  box  was  now  lifted,  and  the  ends  of  the  tubes  extend- 
ing below  it  were  thrust  into  a  bath  of  boiling  oil.  This  set 
the  fluids  into  a  state  of  boiling,  the  purpose  being  to  kill 
any  germs  of  life  that  might  be  accidentally  introduced  into 
them  in  the  course  of  their  conveyance  to  the  test  tubes. 
These  fluids,  exposed  freely  to  the  optically  pure  air  within 
this  chamber,  then  remained  indefinitely  free  from  micro- 
organism^s,  thus  demonstrating  that  putrescible  fluids  may 
be  freely  exposed  to  air  from  which  the  floating  particles 
have  been  removed,  and  not  show  a  trace  either  of  spoiling 
or  of  organic  life  within  them. 

It  might  be  objected  that  the  continued  boiling  of  the 
fluids  had  produced  chemiical  changes  inimical  to  hfc,  or  in 
some  way  destroyed  their  life-supporting  properties;  but 
after  they  had  remained  for  months  in  a  perfectly  clear  state, 
Tyndall  opened  the  little  door  in  the  back  of  the  box  and 
closed  it  at  once,  thereby  admitting  some  of  the  floating 
particles  from  the  outride  air.  Within  a  few  days'  time  the 
fluids  which  previously  had  remained  uncontaminated  were 
spoiling  and  teeming  with  living  organisms. 

These  experim.ents  showed  that  under  the  conditions  of 
the  experiments  no  spontaneous  origin  of  life  takes  place. 
But  while  we  must  regard  the  hypothesis  of  spontaneous 
generation  as  thus  having  been  disproved  on  an  experimental 
basis,  it  is  still  adhered  to  from  the  theoretical  standpoint 
by  many  naturalists;  and  there  are  also  many  who  think 
that  life  arises  spontaneously  at  the  present  time  in  ultra- 
microscopic  particles.  Weismann's  hypothetical  "  biophors," 
too  minute  for  microscopic  observation,  are  supposed  to  arise 
by  spontaneous  generation.     This  phase  of  the  question, 


PASTEUR,    KOCH,    AND    OTHERS  293 

however,  not  being  amenable  to  scientific  tests,  is  theoretical, 
and  therefore,  so  far  as  the  evidence  goes,  we  may  safely  say 
that  the  spontaneous  origin  of  life  under  present  condi- 
tions is  unknown. 

Practical  Applications. — There  are,  of  course,  numerous 
practical  applications  of  the  discovery  that  the  spoiling  of 
putrescible  fluids  is  due  to  floating  germs  that  have  been 
introduced  from  the  air.  One  illustration  is  the  canning  of 
meats  and  fruits,  where  the  object  is,  by  heating,  to  destroy 
all  living  germs  that  are  distributed  through  the  substance, 
and  then,  by  canning,  to  keep  them  out.  When  this  is 
entirely  successful,  the  preserved  vegetables  and  meats  go 
uncontaminated.  One  of  the  most  important  and  practical 
applications  came  in  the  recognition  (1867)  by  the  English 
surgeon  Lister  that  wounds  during  surgical  operations  are 
poisoned  by  floating  particles  in  the  air  or  by  germs  cling- 
ing to  instruments  or  the  skin  of  the  operator,  and  that  to 
render  all  appHances  sterile  and,  by  antiseptic  dressings, 
completely  to  prevent  the  entrance  of  these  bacteria  into 
surgical  wounds,  insures  their  being  clean  and  healthy. 
This  led  to  antiseptic  surgery,  with  which  the  name  of  Lister 
is  indissolubly  connected. 

The  Germ-Theory  of  Disease 

The  germ-theory  of  disease  is  another  question  of  general 
bearing,  and  it  will  be  dealt  with  briefly  here. 

After  the  discovery  of  bacteria  by  Leeuwenhoek,  in  1687, 
some  medical  men  of  the  time  suggested  the  theory  that  con- 
tagious diseases  were  due  to  microscopic  forms  of  life  that 
passed  from  the  sick  to  the  well.  This  doctrine  of  contagium 
vivum,  when  first  promulgated,  took  no  firm  root,  and  grad- 
ually disappeared.  It  was  not  revived  until  about  1840. 
If  we  attempt  briefly  to  sketch  the  rise  of  the  germ-theory  of 


294  BIOLOGY    AND    ITS    MAKERS 

disease,  we  come,  then,  first  to  the  year  1837,  when  the 
Italian  Bassi  investigated  the  disease  of  silkworms,  and 
showed  that  the  transmission  of  that  disease  was  the  result 
of  the  passing  of  minute  glittering  particles  from  the  sick  to 
the  healthy.  Upon  the  basis  of  Bassi's  observation,  the 
distinguished  anatomist  Henle,  in  1840,  expounded  the 
theory  that  all  contagious  diseases  are  due  to  microscopic 
germs. 

The  matter,  however,  did  not  receive  experimental  proof 
until  1877,  when  Pasteur  and  Robert  Koch  showed  the  direct 
connection  between  certain  microscopic  filaments  and  the 
disease  of  splenic  fever,  which  attacks  sheep  and  other  cattle. 
Koch  was  able  to  get  some  of  these  minute  filaments  under 
the  microscope,  and  to  trace  upon  a  warm  stage  the  different 
steps  in  their  germination.  He  saw  the  spores  bud  and 
produce  filamentous  forms.  He  was  able  to  cultivate  these 
upon  a  nutrient  substance,  gelatin,  and  in  this  way  to  obtain 
a  pure  culture  of  the  organism,  which  is  designated  under 
the  term  anthrax.  He  inoculated  mice  with  the  pure  culture 
of  anthrax  germs,  and  produced  splenic  fever  in  the  inocu- 
lated forms.  He  was  able  to  do  this  through  several  genera- 
tions of  mice.  In  the  same  year  Pasteur  showed  a  similar 
connection  between  splenic  fever  and  the  anthrax. 

This  demonstration  of  the  actual  connection  between 
anthrax  and  splenic  fever  formed  the  first  secure  foundation 
of  the  germ-theor}'  of  disease,  and  this  department  of  inves- 
tigation became  an  important  one  in  general  biology.  The 
pioneer  workers  who  reached  the  highest  position  in  the  de- 
velopment of  this  knowledge  are  Pasteur,  Koch,  and  Lister. 

Veneration  of  Pasteur. — Pasteur  is  one  of  the  most  con- 
spicuous figures  of  the  nineteenth  century.  The  veneration 
in  which  he  is  held  by  the  French  people  is  shown  in  the 
result  of  a  popular  vote,  taken  in  1907,  by  which  he  was 
placed  at  the  head  of  all  their  notable  men.     One  of  the  most 


Fig.  92. — Louis  Pasteur  (1822-1895)  and  his  Granddaughter. 


296  BIOLOGY   AND    ITS    MAKERS 

widely  circulated  of  the  French  journals — the  Peiil  Parisien — 
appealed  to  its  readers  all  over  the  country  to  vote  upon  the 
relative  prominence  of  great  Frenchmen  of  the  last  century. 
Pasteur  was  the  winner  of  this  interesting  contest,  having 
received  1,338,425  votes  of  the  fifteen  millions  cast,  and  rank- 
ing above  Victor  Hugo,  who  stood  second  in  popular  esti- 
mation, by  more  than  one  hundred  thousand  votes.  This 
enviable  recognition  was  won,  not  by  spectacular  achieve- 
ments in  arms  or  in  politics,  but  by  indefatigable  industry 
in  the  quiet  pursuit  of  those  scientific  researches  that  have 
resulted  in  so  much  good  to  the  human  race. 

Personal  Qualities. — He  should  be  known  also  from  the 
side  of  his  human  qualities.  He  was  devotedly  attached  to 
his  family,  enjoying  the  close  sympathy  and  assistance  of  his 
wife  and  his  daughter  in  his  scientific  struggles,  a  circum- 
stance that  aided  much  in  ameliorating  the  severity  of  his 
labors.  His  labors,  indeed,  overstrained  his  powers,  so  that 
he  was  smitten  by  paralysis  in  1868,  at  the  age  of  forty-six, 
but  with  splendid  courage  he  overcame  this  handicap,  and 
continued  his  unremitting  work  until  his  death  in  1895. 

The  portrait  of  Pasteur  with  his  granddaughter  (Fig.  92) 
gives  a  touch  of  personal  interest  to  the  investigator  and  the 
contestant  upon  the  field  of  science.  His  strong  face  shows 
dignity  of  purpose  and  the  grim  determination  which  led  to 
colossal  attainments;  at  the  same  time  it  is  mellowed  by 
gentle  affection,  and  contrasts  finely  with  the  trusting  ex- 
pression of  the  younger  face. 

Pasteur  was  born  of  humble  parents  in  D61e  in  the  Jura, 
on  December  the  27th,  1822.  His  father  was  a  tanner, 
but  withal,  a  man  of  fine  character  and  stern  experience,  as 
is  "shown  by  the  fact  that  he  had  fought  in  the  legions 
of  the  First  Empire  and  been  decorated  on  the  field  of 
battle  by  Napoleon."  The  filial  devotion  of  Pasteur  and  his 
justifiable  pride  in  his  father's  military  service  are  shown 


PASTEUR,    KOCH,    AND    OTHERS  297 

in   the  dedication   of  his  book,  Studies  on  Fermentation, 
published  in  1876: 

"To  the  memor}''  of  my  Father, 
Formerly  a  soldier  under  tbe  First  Empire,  and  Knight  of  the  Legion  of 

Honor. 
The  longer  I    live,  the  better  do  I    understand  the  kindness  of  thy  heart 

and  the  superiority  of  thy  judgment. 

The  efforts  which  I  have  devoted  to  these  studies  and  to  those  which  have 

preceded  them  are  the  fruits  of  thy  example  and  of  thy  counsel. 

Desiring  to  honor  these  precious  recollections,  I  dedicate  this  book  to  thy 

memory." 

When  Pasteur  was  an  infant  of  two  years  his  parents 
removed  to  the  town  of  Arbois,  and  here  he  spent  his  youth 
and  received  his  early  education.  After  a  period  of  indiffer- 
ence to  study,  during  which  he  employed  his  time  chiefly  in 
fishing  and  sketching,  he  settled  down  to  work,  and,  there- 
after, showed  boundless  energy  and  enthusiasm. 

Pasteur,  whom  we  are  to  consider  as  a  biologist,  won  his 
first  scientific  recognition  at  the  age  of  twenty-five,  in  chem- 
istry and  molecular  physics.  He  showed  that  crystals  of 
certain  tartrates,  identical  in  chemical  composition,  acted 
differently  upon  polarized  light  transmitted  through  them. 
He  concluded  that  the  differences  in  optical  properties 
depended  upon  a  different  arrangement  of  the  molecules; 
and  these  studies  opened  the  fascinating  field  of  molecular 
physics  and  physical  chemistry. 

Pasteur  might  have  remained  in  this  field  of  investigation, 
but  his  destiny  was  different.  As  Tyndall  remarked,  "In 
the  investigation  of  microscopic  organisms — the  'infinitely 
little,'  as  Pasteur  loved  to  call  them — and  their  doings  in  this, 
our  world,  Pasteur  found  his  true  vocation.  In  this  broad 
field  it  has  been  his  good  fortune  to  alight  upon  a  crowd  of 
connected  problems  of  the  highest  public  and  scientific 
interest,  ripe  for  solution,  and  requiring  for  their  successful 


298  BIOLOGY   AND    ITS   MAKERS 

treatment  the  precise  culture  and  capacities  which  he  has 
brought  to  bear  upon  them." 

In  1857  Pasteur  went  to  Paris  as  director  of  scientific 
studies  in  the  ficole  Normale,  having  previously  been  a 
professor  in  Strasburg  and  in  I.ille.  From  this  time  on  his 
energies  became  more  and  more  absorbed  in  problems  of  a 
biological  nature.  It  was  a  momentous  year  (1857)  in  the 
annals  of  bacteriology  when  Pasteur  brought  convincing 
proof  that  fermentation  (then  considered  chemical  in  its 
nature)  was  due  to  the  growth  of  organic  life.  Again  in  i860 
he  demonstrated  that  both  lactic  (the  souring  of  milk)  and 
alcoholic  fermentation  are  due  to  the  growth  of  microscopic 
organisms,  and  by  these  researches  he  developed  the 
province  of  biology  that  has  expanded  into  the  science  of 
bacteriology. 

After  Pasteur  entered  the  path  of  investigation  of  microbes 
his  progress  was  by  ascending  steps;  each  new  problem  the 
solution  of  which  he  undertook  seemed  of  greater  importance 
than  the  one  just  conquered.  He  was  led  from  the  discovery 
of  microbe  action  to  the  application  of  his  knowledge  to  the 
production  of  antitoxins.  In  all  this  he  did  not  follow  his 
own  inclinations  so  much  as  his  sense  of  a  call  to  service.  In 
fact,  he  always  retained  a  regret  that  he  was  not  permitted 
to  perfect  his  researches  on  crystallography.  At  the  age  of 
seventy  he  said  of  himself:  ''If  I  have  a  regret,  it  is  that  I  did 
not  follow  that  route,  less  rude  it  seems  to  me,  and  which 
would  have  led,  I  am  convinced,  to  wonderful  discoveries. 
A  sudden  turn  threw  me  into  the  study  of  fermentation,  fer- 
mentations set  me  at  diseases,  but  I  am  still  inconsolable  to 
think  that  I  have  never  had  the  time  to  go  back  to  my  old 
subject"  (Tarbell). 

Although  the  results  of  his  combined  researches  form  a 
succession  of  triumphs,  every  point  of  his  doctrines  vras  the 
subject  of  fierce  controversy;    no  investigations  ever  met 


PASTEUR,    KOCH,    AND    OTHERS  299 

with  more  determined  opposition,  no  investigator  ever  fought 
more  strenuously  for  the  estabhshment  of  each  new  truth. 

He  went  from  the  study  of  the  diseases  of  wines  (1865) 
to  the  investigation  (i 865-1 868)  of  the  silkworm  plague 
which  had  well-nigh  crushed  the  silk  industry  of  his  country. 
The  result  was  the  saving  of  millions  of  francs  annually  to 
the  people  of  France. 

His  Supreme  Service. — He  then  entered  upon  his  chief 
services  to  humanity — the  application  of  his  discoveries  to 
the  cure  and  prevention  of  diseases.  By  making  a  succession 
of  pure  cultures  of  a  disease-producing  virus,  he  was  able  to 
attenuate  it  to  any  desired  degree,  and  thereby  to  create  a 
vaccinating  form  of  the  virus  capable  of  causing  a  mild  affec- 
tion of  the  disease.  The  injection  of  this  attenuated  virus 
secured  immunity  from  future  attacks.  The  efficacy  of  this 
form  of  inoculation  was  first  proved  for  the  disease  of  fowl 
cholera,  and  then  came  the  clear  demonstration  (1881)  that 
the  vaccine  was  effective  against  the  splenic  fever  of  cattle. 
Crowning  this  series  of  discoveries  came  the  use  of  inoculation 
(1885)  to  prevent  the  development  of  hydrophobia  in  one 
bitten  by  a  mad  dog. 

The  Pasteur  Institute. — ^The  time  had  now  come  for  the 
establishment  of  an  institute,  not  alone  for  the  treatment  of 
hydrophobia,  but  also  for  the  scientific  study  of  means  to 
control  other  diseases,  as  diphtheria,  typhoid,  tuberculosis, 
etc.  A  movement  was  set  on  foot  for  a  popular  subscription 
to  meet  this  need.  The  response  to  this  call  on  the  part  of 
the  common  people  was  gratifying.  "The  extraordinary  en- 
thusiasm which  accompanied  the  foundation  of  this  great 
institution  has  certainly  not  been  equaled  in  our  time. 
Considerable  sums  of  money  were  subscribed  in  foreign  coun- 
tries, while  contributions  poured  in  from  every  part  of  France. 
Even  the  inhabitants  of  obscure  little  towns  and  villages 
organized  f^tes,  and  clubbed  together  to  send  their  small 


300  BIOLOGY   AND    ITS    MAKERS 

gifts  "  (Franckland).     The  total  sum  subscribed  on  the  date 
of  the  opening  ceremony  amounted  to  3,586,680  francs. 

The  institute  was  formally  opened  on  November  i4t'h, 
1888,  with  impressive  ceremonies  presided  over  by  the 
President  of  the  Republic  of  France.  The  establishment 
of  this  institute  was  an  event  of  great  scientific  importance. 
Here,  within  the  first  decade  of  its  existence,  were  success- 
fully treated  more  than  twenty  thousand  cases  of  hydrophobia. 
Here  has  been  discovered  by  Roux  the  antitoxin  for  diph- 
theria, and  here  have  been  established  the  principles  of  inoc- 
ulation against  the  bubonic  plague,  against  lockjaw,  against 
tuberculosis  and  other  maladies,  and  of  the  recent  microbe 
inoculations  of  Wright  of  London.  More  than  thirty 
*' Pasteur  institutes,"  with  aims  similar  to  the  parent  institu- 
tion, have  been  established  in  different  parts  of  the  civilized 
world. 

Pasteur  died  in  1895,  greatly  honored  by  the  whole  world. 
On  Saturday,  October  5th  of  that  year,  a  national  funeral 
was  conducted  in  the  Church  of  Notre-Dame,  which  was 
attended  by  the  representatives  of  the  state  and  of  numerous 
scientific  bodies  and  learned  societies. 

Koch. — ^Robert  Koch  (Fig.  93)  was  born  in  1843,  ^^^  for 
several  years  before  his  death,  in  19 10,  he  was  the  Director 
of  the  Institute  for  Infectious  Diseases  in  Berlin.  His  studies 
have  been  mainly  those  of  a  medical  man,  and  have  been 
crowned  with  remarkable  success.  In  1881  he  discovered 
the  germ  of  tuberculosis,  in  1883  the  germ  that  produces 
Asiatic  cholera,  and  since  that  time  his  name  has  been  con- 
nected with  a  number  of  remarkable  discoveries  that  are  of 
continuous  practical  application  in  the  science  of  medicine. 

Koch,  with  the  rigorous  scientific  spirit  for  which  he  is 
noteworthy,  established  four  necessary  links  in  the  chain 
of  evidence  to  show  that  a  particular  organism  is  connected 
with  a  particular  disease.    These  four  postulates  of  Koch  are : 


PASTEUR,    KOCH,    AND   OTHERS 


301 


First,  that  a  microscopic  organism  of  a  particular  type  should 
be  found  in  great  abundance  in  the  blood  and  the  tissue  of  the 
sick  animal;  second,  that  a  pure  culture  should  be  made  of 
the  suspected  organism;  third,  that  this  pure  culture,  when 
introduced  into  the  body  of  another  animal,  should  produce 


Fig.  93. — Robert  Koch,  1843-1910. 


the  disease;  and,  fourth,  that  in  the  blood  and  tissues  of  that 
animal  there  should  be  found  quantities  of  the  particular 
organism  that  is  suspected  of  producing  the  disease.  In  the 
case  of  some  diseases  this  entire  chain  of  evidence  has  been 
established ;  but  in  others,  such  as  cholera  and  typhoid  fever, 
the  last  steps  have  not  been  completed,  for  the  reason  that  the 


302  BIOLOGY  AND  ITS  MAKERS 

animals  experimented  upon,  namely,  guinea-pigs,  rabbits, 
and  mice,  are  not  susceptible  to  these  diseases. 

Lister. — The  other  member  of  the  great  triumvirate  of 
bacteriology.  Sir  Joseph  Lister  (Fig.  94),  was  born  in  1827 
and  lived  until  Feby.  11,  191 2;  he  was  successively  professor 


Fig.  94. — Sir  Joseph  Lister,  182 7-19 12. 


of  surgery  in  the  universities  of  Glasgow  (i860)  and  of  Edin- 
burgh (1869),  and  in  King's  College,  London  (1877).  His 
practical  apphcation  of  the  germ-theory  introduced  aseptic 
methods  into  surgery  and  completely  revolutionized  that 
field.  This  was  in  1867.  In  an  address  given  that  year  be- 
fore the  British  Medical  Association  in  Dublin,  he  said: 
"When  it  had  been  shown  by  the  researches  of  Pasteur  that 


PASTEUR,  KOCH,  AND  OTHERS  303 

the  septic  property  of  the  atmosphere  depended,  not  on  oxy- 
gen or  any  gaseous  constituent,  but  on  minute  organisms 
suspended  in  it,  which  owed  their  energy  to  their  vitality,  it 
occurred  to  me  that  decomposition  in  the  injured  part  might 
be  avoided  without  excluding  the  air,  by  applying  as  a  dress- 
ing some  material  capable  of  destroying  the  life  of  the  float- 
ing particles."  At  first  he  used  carbolic  acid  for  this  purpose. 
*'The  wards  of  which  he  had  charge  in  the  Glasgow  Infirm- 
ary were  especially  affected  by  gangrene,  but  in  a  short  time 
became  the  healthiest  in  the  world;  while  other  wards  sepa- 
rated by  a  passageway  retained  their  infection."  The 
method  of  Lister  has  been  universally  adopted,  and  at  the 
same  time  has  been  greatly  extended  and  improved. 

The  question  of  immunity,  i.e.,  the  reason  why  after  hav- 
ing had  certain  contagious  diseases  one  is  rendered  immune, 
is  of  very  great  interest,  but  is  of  medical  bearing,  and 
therefore  is  not  dealt  with  here. 

Schaudinn. — ^During  recent  years  remarkable  advances 
have  been  made  in  the  study  of  protozoa  that  are  connected 
with  human  and  animal  diseases,  and  no  single  observer  has 
contributed  more  eminently  to  these  advances  than  Fritz 
Robert  Schaudinn,  1871-1906  (Fig.  94a).  He  made  impor- 
tant discoveries  and  opened  up  new  lines  of  investigation 
that  are  full  of  promise.  After  studies  on  f oramenif era  ( 1 894) , 
and  nuclear  division  in  other  protozoa  (1896),  he  was  drawn 
to  the  study  of  pathogenic  protozoa,  the  life  history  of  which 
he  followed  with  conspicuous  success.  After  unravelling 
the  complexities  of  the  life-cycle  in  certain  coccidia,  parasitic 
in  the  mole,  he  traced  in  the  human  blood  corpuscles  the 
different  stages  of  the  carriers  of  malaria. 

In  1901,  under  the  auspices  of  the  Imperial  Health  Bureau 
(Kaiserl-Gesundheitsamtes)  of  Berlin,  he  went  to  the  station 
at  Rovigno,  and  thereafter  to  the  end  of  his  life,  he  devoted 


304 


BIOLOGY  AND   ITS  MAKERS 


his  energies  to  the  study  of  pathogenic  protozoa  and  of  some 
bacteria.  He  observed  the  successive  stages  of  generation 
of  some  micro-organisms  of  birds  and  other  animals,  and 
in  1905,  he  clearly  demonstrated  the  spirochaete  of  syphilis 
{Treponema  pallida)  the  existence  of  which  had  previously 
been  made  known  by  Siegel. 


Fig.  94a. — Fritz  Schaudinn,  1871-1906. 


His  researches  were  thorough  as  well  as  brilliant,  and  it  is 
largely  owing  to  his  influence  that  the  importance  of  proto- 
zoology is  recognized  as  a  special  division  of  biological  study. 

Bacteria  and  Nitrates. — One  further  illustration  of  the 
connection  between  bacteria  and  practical  affairs  may  be 
mentioned.  It  is  well  known  that  animals  are  dependent 
upon  plants,  and  that  plants  in  the  manufacture  of  protoplasm 
make  use  of  certain  nitrites  and  nitrates  which  they  obtain 


PASTEUR,  KOCH,  AND  OTHERS  305 

from  the  soil.  Now,  the  source  of  these  nitrites  and  nitrates 
is  very  interesting.  In  animals  the  final  products  of  broken- 
down  protoplasm  are  carbon  dioxide,  water,  and  a  nitrog- 
enous substance  called  urea.  These  products  are  called 
excretory  products.  The  animal  machine  is  unable  to  utilize 
the  energy  which  exists  in  the  form  of  potential  energy  in 
these  substances,  and  they  are  removed  from  the  body. 

The  history  of  nitrogenous  substance  is  the  one  which  at 
present  interests  us  the  most.  Entering  the  soil,  it  is  there 
acted  upon  by  bacteria  residing  in  the  soil,  these  bacteria 
possessing  the  power  of  making  use  of  the  lowest  residuum 
of  energy  left  in  the  nitrogenous  substance.  They  cause  the 
nitrogen  and  the  hydrogen  to  unite  with  oxygen  in  such  a  way 
that  there  are  produced  nitrous  and  nitric  acids,  and  from 
these  two  acids,  through  chemical  action,  result  the  nitrites  and 
the  nitrates.  These  substances  are  then  utilized  by  the  plant 
in  the  manufacture  of  protoplasm,  and  the  plant  is  fed  upon 
by  animal  organisms,  so  that  a  direct  relationship  is  estab- 
lished between  these  lower  forms  of  life  and  the  higher  plant 
and  animal  series;  a  relationship  that  is  not  only  interesting, 
but  that  helps  to  throw  an  important  side-light  upon  the 
general  nature  of  vital  activities,  their  kind  and  their  reach. 
In  addition  to  the  soil  bacteria  mentioned  above,  there 
are  others  that  form  association  with  the  rootlets  of  certain 
plants  and  possess  the  power  of  fixing  free  nitrogen  from 
the  air. 

The  nitrifying  bacteria,  are,  of  course,  of  great  importance 
to  the  farmer  and  the  agriculturist. 

It  is  not  our  purpose,  however,  to  trace  the  different 
phases  of  the  subject  of  bacteriology  to  their  conclusions,  but 
rather  to  give  a  picture  of  the  historical  development  of  this 
subject  as  related  to  the  broader  one  of  general  biology. 


CHAPTER  XIV 

HEREDITY  AND  GERMINAL  CONTINUITY— 
MENDEL,  GALTON,  WEISMANN 

It  is  a  matter  of  common  observation  that  in  the  living 
world  like  tends  to  produce  like.  The  offspring  of  plants, 
as  well  as  of  animals,  resembles  the  parent,  and  among  all 
organisms  endowed  with  mind,  the  mental  as  well  as  the 
physical  qualities  are  inherited.  This  is  a  simple  statement 
of  the  fact  of  heredity,  but  the  scientific  study  of  inheritance 
involves  deep-seated  biological  questions  that  emerged  late 
in  the  nineteenth  century,  and  the  subject  is  still  in  its 
infancy. 

In  investigating  this  question,  we  need  first,  if  possible, 
to  locate  the  bearers  of  hereditary  qualities  within  the  physical 
substance  that  connects  one  generation  with  the  next;  then, 
to  study  their  behavior  during  the  transmission  of  life  in  order 
to  account  for  the  inheritance  of  both  maternal  and  paternal 
qualities;  and,  lastly,  to  determine  whether  or  not  transiently 
acquired  characteristics  are  inherited. 

Hereditary  Qualities  in  the  Germinal  Elements. — When 
we  take  into  consideration  the  fact  established  for  all  animals 
and  plants  (setting  aside  cases  of  budding  and  the  division 
of  unicellular  organisms),  that  the  only  substance  that  passes 
from  one  generation  to  another  is  the  egg  and  the  sperm  in 
animals,  and  their  representatives  in  plants,  we  see  that  the 
first  question  is  narrowed  to  these  bodies.  If  all  hereditary 
qualities  are  carried  in  the  egg  and  the  sperm — as  it  seems 
they  must  be — then  it  follows  that  these  germinal  elements, 

306 


HEREDITY  AND  GERMINAL  CONTINUITY  307 

although  microscopic  in  size,  have  a  very  complex  organiza- 
tion. The  discovery  of  this  organization  must  depend  upon 
microscopic  examination.  Knowledge  regarding  the  physical 
basis  of  heredity  has  been  greatly  advanced  by  critical  studies 
of  cells  under  the  microscope  and  by  the  application  of  ex- 
perimental methods,  while  other  phases  of  the  problems  of 
inheritance  have  been  elucidated  by  the  analysis  of  statistics 
regarding  hereditary  transmissions.  The  whole  question, 
however,  is  so  recent  that  a  clear  formulation  of  the  direction 
of  the  main  currents  of  progress  will  be  more  helpful  than 
any  attempt  to  estimate  critically  the  underlying  principles. 

Early  Theories. — There  were  speculations  regarding  the 
nature  of  inheritance  in  ancient  and  mediaeval  times.  To 
mention  any  of  them  prior  to  the  eighteenth  century  would 
serve  no  useful  purpose,  since  they  were  vague  and  did  not 
form  the  foundation  upon  which  the  modern  theories  were 
built.  The  controversies  over  pre-formation  and  epigenesis 
(see  Chapter  X)  of  the  eighteenth  century  embodied  some 
ideas  that  have  been  revived.  The  recent  conclusion  that 
there  is  in  the  germinal  elements  an  inherited  organization 
of  great  complexity  which  conditions  inheritance  seems,  at 
first,  to  be  a  return  to  the  doctrine  of  pre-formation,  but  closer 
examination  shows  that  there  is  merely  a  general  resemblance  / 
between  the  ideas  expressed  by  Haller,  Bonnet,  and  philos- 
ophers of  their  time  and  those  current  at  the  present  time. 
Inherited  organization,  as  now  understood,  is  founded  on 
the  idea  of  germinal  continuity  and  is  vastly  different  from 
the  old  theory  of  pre-formation.  The  meaning  of  epigenesis, 
as  expressed  by  Wolff,  has  also  been  modified  to  include  the 
conception  of  pre-localization  of  hereditary  qualities  w^ithin 
particular  parts  of  the  egg.  It  has  come  now  to  mean  that 
development  is  a  process  of  difi"erentiation  of  certain  qualities 
already  laid  down  in  the  germinal  elements. 

Darwin's    Theory    of    Pangenesis. — In    attempting    to 


3o8  BIOLOGY  AND  ITS  MAKERS 

account  for  heredity,  Darwin  saw  clearly  the  necessity  of 
providing  some  means  of  getting  all  hereditary  qualities  com- 
bined within  the  egg  and  the  sperm.  Accordingly  he  orig- 
inated his  provisional  theory  of  pangenesis.  Keeping  in  mind 
the  fact  that  all  organism.s  begin  their  lives  in  the  condition 
of  single  cells,  the  idea  of  inheritance  through  these  micro- 
scopic particles  becomes  difficult  to  understand.  How  is  it 
possible  to  conceive  of  all  the  hereditary  qualities  being  con- 
tained within  the  microscopic  germ  of  the  future  being? 
Darwin  supposed  that  very  minute  particles,  which  he  called 
gemmules,  were  set  free  from  all  the  cells  in  the  body,  those 
of  the  muscular  system,  of  the  nervous  system,  of  the  bony 
tissues,  and  of  all  other  tissues  contributing  their  part.  These 
liberated  gemmules  were  supposed  to  be  carried  by  the  cir- 
culation and  ultimately  to  be  aggregated  within  the  germinal 
elements  (ovum  and  sperm).  Thus  the  germinal  elements 
would  be  a  composite  of  substances  derived  from  all  organs 
and  all  tissues. 

With  this  conception  of  the  blending  of  the  parental 
qualities  within  the  germinal  elements  we  can  conceive  how 
inheritance  would  be  possible  and  how  there  might  be  in- 
cluded in  the  egg  and  the  sperm  a  representative  in  material 
substance  of  all  the  qualities  of  the  parents.  Since  develop- 
ment begins  in  a  fertilized  ovum,  this  complex  would  contain 
minute  particles  derived  from  every  part  of  the  bodies  of 
both  parents,  which  by  growth  would  give  rise  to  new  tissues, 
all  of  them  containing  representatives  of  the  tissues  of  the 
parent  form. 

Theory  of  Pangenesis  Replaced  by  that  of  Germinal  Con- 
tinuity.— This  theory  of  Darwin  served  as  the  basis  for  other 
theories  founded  upon  the  conception  of  the  existence  of  pan- 
gens  ;  and  although  the  modifications  of  Spencer,  Brooks,  and 
others  were  important,  it  is  not  necessary  to  indicate  them  in 
detail  in  order  to  understand  what  is  to  follow.     The  various 


HEREDITY  AND  GERMINAL  CONTINUITY  309 

theories  founded  upon  the  idea  of  pangens  were  destined  to 
be  replaced  by  others  founded  on  the  conception  of  geminal 
continuity — the  central  idea  in  nineteenth-century  biology. 

The  four  chief  steps  which  have  led  to  the  advancement 
of  the  knowledge  of  heredity,  as  suggested  by  Thomson,  are 
as  follows:  "  (a)  The  exposition  of  the  doctrine  of  germinal 
continuity,  (b)  More  precise  investigation  of  the  material 
basis  of  inheritance,  (c)  Suspicions  regarding  the  inherit- 
ance of  acquired  characteristics,  (d)  Application  of  statis- 
tical methods  which  have  led  to  the  formulation  of  the  law 
of  ancestral  heredity."     We  shall  take  these  up  in  order. 

Exposition  of  the  Doctrine  of  Germinal  Continuity. — 
From  parent  to  offspring  there  passes  some  hereditary  sub- 
stance; although  small  in  amount,  it  is  the  only  living  thread 
that  connects  one  generation  with  another.  It  thus  appears 
that  there  enters  into  th-e  building  of  the  body  of  a  new  organ- 
ism some  of  the  actual  substance  of  both  parents,  and  that 
this  transmitted  substance  must  be  the  bearer  of  hereditary 
qualities.  Does  it  also  contain  some  characteristics  inherited 
from  grandparents  and  previous  generations?  If  so,  how 
far  back  in  the  history  of  the  race  does  unbroken  continuity 
extend  ? 

Briefly  stated,  genetic  continuity  means  that  the  ovum 
and  its  fertilizing  agent  are  derived  by  continuous  cell-lineage 
from  the  fertilized  ovum  of  previous  generations,  extending 
back  to  the  beginning  of  life.  The  first  clear  exposition  of 
this  theory  occurs  in  the  classical  work  of  Virchow  on  Cellular 
Pathology,  pubhshed  in  1858.  Virchow  (1821-1902),  the 
distinguished  professor  of  the  University  of  Berlin,  has  al- 
ready been  spoken  of  in  connection  with  the  development 
of  histology.  He  took  the  step  of  overthrowing  the  theory 
of  free  cell-formation,  and  replacing  it  by  the  doctrine  of 
cell- succession.  According  to  the  theory  of  Schleiden  and 
Schwann,  cells  arose  from  a  blastema  by  a  condensation  of 


3IO  BIOLOGY  AND  ITS  MAKERS 

matter  around  a  nucleus,  and  the  medical  men  prior  to  1858 
believed  in  free  cell-formation  within  a  matrix  of  secreted 
or  excreted  substance.  This  doctrine  was  held  with  tenacity 
especially  for  pathological  growths.  Virchow  demonstrated, 
however,  that  there  is  a  continuity  of  living  substance  in  all 
growths — that  cells,  both  in  health  and  in  disease,  arise  only 
by  the  growth  and  division  of  previously  existing  living  cells; 
and  to  express  this  truth  he  coined  the  formula  ^^  omnis 
cellula  e  cellula.^'  Manifestly  it  vras  necessary  to  establish 
this  law  of  cell- succession  before  any  idea  of  germinal  con- 
tinuity could  prevail.  Virchow' s  work  in  this  connection 
is  of  undying  value. 

When  applied  to  inheritance  the  idea  of  the  continuity  of 
living  substance  leads  to  making  a  distinction  between  germ- 
cells  and  body-cells.  This  had  been  done  before  the  obser- 
vations of  Virchow  made  their  separation  of  great  theoretical 
value.  Richard  Owen,  in  1849,  pointed  out  certain  differ- 
ences between  the  body-cells  and  the  germinal  elements, 
but  he  did  not  follow  up  the  distinction  which  he  made. 
Haeckel's  General  Morphology,  published  in  1866,  forecasts 
the  idea  also,  and  in  1878  Jaeger  made  use  of  the  phrase 
"continuity  of  the  germ  protoplasm."  Other  suggestions 
and  modifications  led  to  the  clear  expression  by  Nussbaum, 
about  1875,  that  the  germinal  substance  was  continued  by 
unbroken  generations  from  the  past,  and  is  the  particular 
substance  in  which  all  hereditary  qualities  are  included. 
But  the  conception  finds  its  fullest  expression  in  the  work 
of  Weismann. 

Weismann's  explanation  of  heredity  is  at  first  sight 
relatively  simple.  In  reply  to  the  question,  "Why  is  the 
offspring  like  the  parent ? "  he  says,  "Because  it  is  composed 
of  some  of  the  same  stuff."  In  other  words,  there  has  been 
unbroken  germinal  continuity  between  generations.  His  idea 
of  germinal  continuity,  i.e.,  unbroken  continuity,  through  all 


HEREDITY  AND  GERMINAL  CONTINUITY  311 

time,  of  the  germinal  substance,  is  a  conception  of  very  great 
extent,  and  now  underlies  all  discussion  of  heredity. 

In  order  to  comprehend  it,  we  must  first  distinguish 
between  the  germ-cells  and  the  body-cells.  Weismann 
regards  the  body,  composed  of  its  many  cells,  as  a  derivative 
that  becomes  simply  a  vehicle  for  the  germ-cells.  Owen's 
distinction  between  germ-cells  and  body-cells,  made  in  1849, 
was  not  of  much  importance,  but  in  the  theory  of  Weismann 
it  is  of  vital  significance.  The  germ-cells  are  the  particular 
ones  which  carry  forward  from  generation  to  generation  the 
life  of  the  individual.  The  body-cells  are  not  inherited  di- 
rectly, but  in  the  transmission  of  life  the  germ-cells  pass  to 
the  succeeding  generation,  and  they  in  turn  have  been  inher- 
ited from  the  previous  generation,  and,  therefore,  we  have 
the  phenomenon  of  an  unbroken  connection  with  all  previous 
generations. 

When  the  full  significance  of  this  conception  comes  to  us, 
we  see  why  the  germ-cells  have  an  inherited  organization  of 
remarkable  complexity.  This  germinal  substance  embodies 
all  the  past  history  of  the  living,  impressionable  protoplasm, 
which  has  had  an  unbroken  series  of  generations.  During 
all  time  it  has  been  subjected  to  the  molding  influence  of 
external  circumstances  to  which  it  has  responded,  so  that 
the  summation  of  its  experiences  becomes  in  some  way 
embedded  within  its  material  substance.  Thus  we  have 
the  germinal  elements  possessing  an  inherited  organization 
made  up  of  all  the  previous  experiences  of  the  protoplasm, 
some  of  which  naturally  are  much  more  dominant  than  the 
others. 

We  have  seen  that  this  idea  was  not  first  expressed  by 
Weismann;  it  was  a  modification  of  the  views  of  Nussbaum 
and  Hertwig.  While  it  was  not  his  individually,  his  con- 
clusions were  apparently  reached  independently.  This  idea 
was  in  the  intellectual  atmosphere  of  the  times.     Several 


312  BIOLOGY  AND  ITS  MAKERS 

investigators  reached  their  conclusions  independently,  al- 
though there  is  great  similarity  between  them.  Although  the 
credit  for  the  first  formulation  of  the  law  of  germinal  con- 
tinuity does  not  belong  to  Weismann,  that  of  the  greatest 
elaboration  of  it  does.  This  doctrine  of  germinal  continuity 
is  now  so  firmly  embedded  in  biological  ideas  of  inheritance 
and  the  evolution  of  animal  life  that  we  may  say  it  has  become 
the  corner-stone  of  modern  biology. 

The  conclusion  reached — that  the  hereditary  substance  is 
the  germ-plasm — is  merely  prehminary ;  the  question  remains, 
Is  the  germ-plasm  homogeneous  and  endowed  equally  in  all 
parts  with  a  mixture  of  hereditary  qualities  ?  This  leads 
to  the  second  step. 

The  More  Precise  Investigation  of  the  Material  Basis  of 
Inheritance. — The  application  of  the  microscope  to  critical 
studies  of  the  structure  of  the  germ-plasm  has  brought 
important  results  which  merge  with  the  development  of  the 
idea  of  germinal  continuity.  Can  we  by  actual  observation 
determine  the  particular  part  of  the  protoplasmic  substance 
that  carries  the  hereditary  qualities?  The  earliest  answer 
to  this  question  was  that  the  protoplasm,  being  the  living 
substance,  was  the  bearer  of  heredity.  But  close  analysis 
of  the  behavior  of  the  nucleus  during  development  led, 
about  1875,  to  the  idea  that  the  liereditary  qualities  are  located 
within  the  nucleus  of  the  cell. 

This  idea,  promulgated  by  Fol,  Koelliker,  and  Oskar 
Hertwig,  narrowed  the  attention  of  students  of  heredity 
from  the  general  protoplasmic  contents  of  the  cell  to  the 
nucleus.  Later  investigations  show  that  this  restriction  was, 
in  a  measure,  right.  The  nucleus  takes  an  active  part 
during  cell-division,  and  it  was  very  natural  to  reach  the 
conclusion  that  it  is  the  particular  bearer  of  hereditary 
substance.  But,  in  1883,  Van  Beneden  and  Boveri  made 
the   discovery   that   within   the    nucleus    are    certain    dis- 


HEREDITY  AND  GERMINAL  CONTINUITY  313 

tinct  little  rod-like  bodies  which  make  their  appearance 
during  cell-division.  These  little  bodies,  inasmuch  as  they 
stain  very  deeply  with  the  dyes  used  in  microscopic  re- 
search, are  called  chromosomes.  And  continued  investigation 
brought  out  the  astounding  fact  that,  although  the  number  of 
chromosomes  vary  in  different  animals  (commonly  from  two 
to  twenty-four),  they  are  of  the  same  number  in  all  the  cells 
of  any  particular  animal  or  plant.  These  chromosomes  are 
regarded  as  the  bearers  of  heredity,  and  their  behavior  during 
fertilization  and  development  has  been  followed  with  great 
care. 

Brilliant  studies  of  the  formation  of  the  egg  have 
shown  that  the  egg  nucleus,  in  the  process  of  becoming 
mature,  surrenders  one-half  its  number  of  chromosomes;  it 
approaches  the  surface  of  the  egg  and  undergoes  division, 
squeezing  out  one-half  of  its  substance  in  the  form  of  a  polar 
globule;  and  this  process  is  once  repeated.*  The  formation 
of  polar  globules  is  accompanied  by  a  noteworthy  process  of 
reduction  in  the  number  of  chromosomes,  so  that  when  the 
egg  nucleus  has  reached  its  mature  condition  it  contains  only 
one-half  the  number  of  chromosomes  characteristic  of  the 
species,  and  will  not  ordinarily  undergo  development  without 
fertilization. 

The  precise  steps  in  the  formation  of  the  sperm  have  also 
been  studied,  and  it  has  been  determined  that  a  parallel 
series  of  changes  occur.  The  sperm,  when  it  is  fully  formed, 
contains  also  one-half  the  number  of  chromosomes  charac- 
teristic of  the  species.  Now,  egg  and  sperm  are  the  two  ger- 
minal elements  which  unite  in  development.  Fertilization 
takes  place  by  the  union  of  sperm  and  egg,  and  inasmuch 
as  the  nuclei  of  each  of  these  structures  contain  one-half  of 
the  number  of  chromosomes  characteristic  of  the  species, 

*  There  are  a  few  exceptions  to  this  rule,  as  in  the  eggs  of  plant-lice, 
etc.,  in  which  a  single  polar  globule  is  produced. 


314  BIOLOGY  AND  ITS  MAKERS 

their  union  in  fertilization  results  in  the  restoration  of  the 
original  number  of  chromosomes.  The  fertilized  ovum  is 
the  starting-point  of  a  new  organism,  and  from  the  method 
of  its  fertilization  it  appears  that  the  parental  qualities  are 
passed  along  to  the  cells  of  every  tissue. 

The  complex  mechanism  exhibited  in  the  nucleus  during 
segmentation  is  very  wonderful.  The  fertilized  ovum  begins 
to  divide,  the  nucleus  passing  through  a  series  of  complicated 
changes  whereby  its  chromosomes  undergo  a  lengthwise 
division — a  division  that  secures  an  equable  partition  of  the 
substance  of  which  they  are  composed.  With  each  successive 
division,  this  complicated  process  is  repeated,  and  the  many 
cells,  arising  from  continued  segmentation  of  the  original  cell, 
contain  nuclei  in  which  are  embedded  descendants  of  the 
chromosomes  in  unbroken  succession.  Moreover,  since  these 
chromosomes  are  bi-parental,  we  can  readily  understand  that 
every  cell  in  the  body  carries  both  maternal  and  paternal 
qualities. 

The  careful  analysis  of  the  various  changes  within  the 
nuclei  of  the  egg  proves  to  be  the  key  to  some  of  the  central 
questions  of  heredity.  We  see  the  force  of  the  point  which 
was  made  in  a  previous  chapter,  that  inheritance  is  in  the 
long  run  a  cellular  study,  and  we  see  in  a  new  light  the  im- 
portance of  the  doctrine  of  germinal  continuity.  This  con- 
ception, in  fact,  elucidates  the  general  problem  of  inheritance 
in  a  way  in  which  it  has  never  been  elucidated  by  any  other 
means. 

For  some  time  the  attention  of  investigators  was  concen- 
trated upon  the  nucleus  and  the  chromosomics,  but  it  is  now 
necessary  to  admit  that  the  basis  of  some  structures  is  dis- 
coverable within  the  cytoplasm  that  surrounds  the  nucleus. 
Experimental  observations  (Conklin,  Lillie,  Wilson)  have 
shown  the  existence  of  particular  areas  within  the  apparently 
simple  substance  of  the  egg,  areas  which  are  definitely  related 


HEREDITY  AND   GERMINAL  CONTINUITY  315 

to  the  development  of  particular  parts  of  the  embryo.  The 
removal  of  any  one  of  these  pre-localized  areas  prevents  the 
development  of  the  part  with  which  it  is  genetically  related. 
Researches  of  this  kind,  necessitating  great  ingenuity  in 
method  and  great  talents  in  the  observers,  are  widening  the 
field  of  observation  upon  the  phenomena  of  heredity. 

The  Inheritance  of  Acquired  Characters. — The  belief  in 
the  inheritance  of  acquired  characteristics  was  generally 
accepted  up  to  the  middle  of  the  nineteenth  century,  but  the 
reaction  against  it  started  by  Galton  and  others  has  assumed 
great  proportions.  Discussions  in  this  Hne  have  been  carried 
on  extensively,  and  frequently  in  the  spirit  of  great  partizan- 
ship.  These  discussions  cluster  very  much  about  the  name 
and  the  work  of  Weismann,  the  man  who  has  consistently 
stood  against  the  idea  of  the  inheritance  of  acquired  charac- 
ters. More  in  reference  to  this  phase  of  the  question  is  given 
in  the  chapter  dealing  with  Weismann's  theory  of  evolution 
(see  p.  398).  Wherever  the  truth  may  lie,  the  discussions 
regarding  the  inheritance  of  acquired  characteristics  pro- 
voked by  Weismann's  theoretical  considerations,  have  re- 
sulted in  stimulating  experiment  and  research,  and  have, 
therefore,  been  beneficial  to  the  advance  of  science.  n 

The  Application  of  Experimental  and  Statistical  Methods 
to  the  Study  of  Heredity.  Mendel. — The  earliest  experi- 
mental investigations  of  heredity  were  conducted  with  plants, 
and  the  first  epoch-making  results  were  those  of  Gregor  Men- 
del (182  2-1884)  (Fig.  95),  a  monk,  and  later  abbot,  of  an 
Augustinian  monastery  at  Brunn,  Austria.  In  the  garden 
of  the  monastery,  for  eight  years  before  pubhshing  his  re- 
sults, he  made  experiments  on  the  inheritance  of  individual 
(or  unit)  characters  in  twenty-two  varieties  of  garden  peas. 
Selecting  certain  constant  and  obvious  characters,  as  color 
and  form  of  seeds,  length  of  stem,  etc.,  he  proceeded  to  cross 
these  pure  races,  thus  producing  hybrids,  and,  thereafter, 


3i6 


BIOLOGY  AND   ITS  MAKERS 


to  observe  the  results  of  self-fertilization  among  the  hybrids. 
The  hybrids  were  produced  by  removing  the  unripe  sta- 
mens of  certain  flowers  and  later  fertilizing  them  by  ripe 
pollen  from  another  pure  breed  having  a  contrasting  charac- 
ter.    The  results  showed  that  only  one  of  a  pair  of  unit 


Fig.  95. — Gregor  Mendel,   1822-1884. 
Permission  of  Professor  Bateson. 

characters  appeared  in  the  hybrids,  while  the  other  contrast- 
ing character  lay  dormant.  Thus,  in  crossing  a  yellow-seeded 
with  a  green-seeded  pea,  the  hybrid  generation  showed  only 
yellow  seeds.  The  character  impressing  itself  on  the  entire 
progeny  was  called  dominant,  while  the  other  that  was  held 
in  abeyance  was  designated  recessive.     That  the  recessive 


HEREDITY  AND    GERMINAL   CONTINUITY  317 

color  was  not  blotted  out  was  clearly  demonstrated  by  allow- 
ing the  hybrid  generation  to  develop  by  self-fertilization. 
Under  these  circumstances  a  most  interesting  result  was  at- 
tained. The  filial  generation,  derived  by  self-fertilization 
among  the  hybrids,  produced  plants  with  yellow  and  green 
seeds,  but  in  the  ratio  of  three  of  the  yellow  to  one  of  the 
green.  All  of  the  green-seeded  individuals  and  one-third  of 
the  yellow  proved  to  breed  true,  while  the  remaining  two- 
thirds  of  yellow-seeded  plants,  when  self-fertilized,  produced 
yellow  and  green  seeds  in  the  ratio  of  three  to  one.  Subse- 
quent breedings  gave  an  unending  series  of  results  similar 
to  those  of  the  first  filial  generation.  This  great  principle 
of  alternative  inheritance  was  exhibited  throughout  the  ex- 
tensive experiments  of  Mendel,  and  it  is  now  recognized 
as  one  of  the  great  biological  discoveries  of  the  nineteenth 
century.  Mr.  R.  C.  Punnett  gives  (1905)  a  remarkably  clear 
and  terse  statement  of  the  facts  as  follows:  ''Whenever  there 
occurs  a  pair  of  differentiating  characters,  of  which  one  is 
dominant  to  the  other,  three  possibilities  exist:  there  are 
recessives  which  always  breed  true  to  the  recessive  character; 
there  are  dominants  which  breed  true  to  the  dominant  char- 
acter, and  are  therefore  pure;  and  thirdly,  there  are  domi- 
nants which  may  be  called  impure,  and  which  on  self-fertiliza- 
tion (or  in  breeding,  where  the  sexes  are  separate)  give  both 
dominant  and  recessive  forms  in  the  fixed  proportion  of  three 
of  the  former  to  one  of  the  latter." 

The  results  of  Mendel's  experiments  are  the  consequence 
of  the  fact  that  the  germ-cells  retain  their  purity  with  respect 
to  unit  characters.  That  is,  in  the  combination  of  germ-cells 
by  cross-breeding,  the  hereditary  qualities  do  not  lose  their 
individuality — they  are  mixed  but  not  blended.  When  the 
germinal  elements  are  formed  in  these  hybrid  plants  two 
classes  of  germ-cells  will  arise  in  equal  number,  one  class 
carrying  the  dominant,  and  the  other  the  recessive  quality. 


3l8  BIOLOGY  AND  ITS  MAKERS 

Chance  combinations  of  these  germ-cells  will  yield  on  the 
average,  one  union  of  dominant  with  dominant,  one  union  of 
recessive  with  recessive,  and  two  combinations  in  which 
dominant  and  recessive  are  united.  In  the  latter  instance  the 
dominant  will  be  the  visible  character,  the  recessive,  though 
present,  being  invisible.  This  segregation  of  the  gametes 
into  two  sets  of  ''pure"  gametes  was  recognized  by  Mendel 
in  an  attempted  theoretical  explanation  of  his  observed  facts, 
and,  in  view  of  the  state  of  knowledge  at  the  time,  showed 
remarkable  analytical  ability. 

Mendel's  papers  were  published  in  1866  and  1867  in  the 
Proceedings  of  the  Natural  History  Society  of  Briinn,  but 
their  importance  was  overlooked  for  nearly  thirty-five  years. 
The  periodical  in  which  they  appeared  was  not  widely  known, 
and  moreover,  the  minds  of  naturalists  at  that  time  were 
largely  occupied  with  the  questions  of  organic  evolution 
raised  through  the  pubHcations  of  Darwin.  In  the  year 
1900,  however,  the  great  principle  of  heredity  worked  out 
by  Mendel  was  independently  re-discovered  by  the  botanists 
DeVries,  Torrens,  and  Tschermak.  By  searching  the  htera- 
ture  for  anticipations  of  their  results,  the  unrecognized  papers 
of  Mendel  were  brought  to  light  and  made  generally  known 
to  the  scientific  world. 

Since  1900,  extensive  experiments  by  Bateson  and  others 
have  served  to  confirm  and  extend  Mendel's  discovery.  In 
the  United  States  the  experiments  of  Davenport  and  Castle 
on  inheritance  in  poultry,  the  inheritance  of  fur  in  guinea-pigs, 
of  erectness  of  ears  of  rabbits,  etc.,  as  well  as  the  experimental 
work  of  others,  has  extended  our  knowledge  of  Mendelian 
inheritance.  The  combined  work  on  inheritance  in  animals 
and  plants  of  all  observers  has  so  thoroughly  supported 
Mendel's  conclusions,  that  the  principle  of  alternative  in- 
heritance is  commonly  spoken  of  as  Mendel's  law. 

Rank  of  MendePs  Discovery. — The  discovery  by  Mendel 


HEREDITY  AND  GERMINAL  CONTINUITY  319 

of  alternative  inheritance  will  rank  as  one  of  the  greatest 
discoveries  in  the  study  of  heredity.  The  fact  that  in  cross- 
breeding the  parental  qualities  are  not  blended,  but  that  they 
retain  their  individuahty  in  the  offspring,  has  many  possible 
practical  applications  both  in  horticulture  and  in  the  breed- 
ing of  animals.  The  germ-cells  of  the  hybrids  have  the  domi- 
nant and  the  recessive  characters  about  equally  divided;  this 
will  appear  in  the  progeny  of  the  second  generation,  and  the 
races,  when  once  separated,  may  be  made  to  breed  true. 

Mendel's  name  was  not  recognized  as  a  prominent  one 
in  the  annals  of  biological  history  until  the  re-discovery  of  his 
law  in  1900;  but  now  he  is  accorded  high  rank. 

Galton. — Francis  Galton,  by  directing  attention  to  the 
inheritance  of  individual  characters  made  the  subject  of 
heredity  manageable.  Previously,  hereditary  traits  had  been 
considered  in  their  entirety,  and  the  resemblances  and  differ- 
ences of  parents  and  their  offspring  had  been  averaged. 
This  method  was  too  diffuse,  since  no  one  could  distinguish 
sharply  among  the  multiplicity  of  characters,  and  it  was 
a  great  forward  step  when  Galton  began  to  study  hereditary 
characters  separately.  ''At  the  same  time  that  Galton  was 
thus  laying  the  foundation  for  a  scientific  study  of  heredity 
by  dealing  with  characters  separately,  another  and  even 
greater  student  of  heredity,  Gregor  Mendel,  was  doing  the 
same  thing  in  his  experiments  with  garden  peas.  But  inas- 
much as  Mendel's  work  remained  practically  unknown  for 
many  years,  Galton  has  been  rightly  recognized  as  the  founder 
of  the  scientific  study  of  heredity"  (Conklin,  1915). 

Galton,  182 2-19 1 1  (Fig.  96),  was  the  grandson  of  Doctor 
Erasmus  Darwin  and  the  half  cousin  of  Charles.  After  pub- 
lishing books  on  his  travels  in  Africa,  he  began  the  experi- 
mental study  of  heredity  and,  in  187 1,  he  read  before  the 
Royal  Society  of  London  a  paper  on  Pangenesis,  in  which  he 
departed  from  that  theory  as  developed  by  Darwin.     The 


320  BIOLOGY  AND  ITS  MAKERS 

observations  upon  which  he  based  his  conclusions  were  made 
upon  the  transfusion  of  blood  in  rabbits  and  their  after- 
breeding.    He  studied  the  inheritance  of  stature,  and  other 


Fig.  96. — Francis  Galton,  1822-1911. 

characteristics,  in  human  families,  and  the  inheritance  of 
spots  on  the  coat  of  certain  hounds,  and  was  led  to  formulate 
a  law  of  ancestral  inheritance  which  received  its  clearest  ex- 
pression in  his  book,  Natural  Inheritance,  published  in  1889. 

He  undertook  to  determine  the  proportion  of  heritage 
that  is,  on  the  average,  contributed  by  each  parent,  grand- 


HEREDITY  AND  GERMINAL  CONTINUITY  321 

parent,  etc.,  and  arrived  at  the  following  conclusions:  "The 
parents  together  contribute  one-half  the  total  heritage,  the 
four  grandparents  together  one-fourth,  the  eight  great-grand- 
parents one-sixteenth,  and  all  the  remainder  of  the  ancestry 
one-sixteenth." 

Karl  Pearson  has  investigated  this  law  of  ancestral  inher- 
itance. He  substantiates  the  law  in  its  principle,  but  modifies 
slightly  the  mathematical  expression  of  it. 

This  field  of  research,  which  involves  measurements  and 
mathematics  and  the  handling  of  large  bodies  of  statistics, 
has  been  considerably  cultivated,  so  that  there  is  in  existence 
in  England  a  journal  devoted  exclusively  to  biometrics,  which 
is  edited  by  Karl  Pearson,  and  is  entitled  Biometrika. 

The  whole  subject  of  heredity  is  undergoing  a  thorough 
revision.  What  seems  to  be  most  needed  at  the  present  time 
is  more  exact  experimentation,  carried  through  several  gen- 
erations, together  with  more  searching  investigations  into 
the  microscopical  constitution  of  egg  and  sperm,  and  close 
analysis  of  just  what  takes  place  during  fertilization  and  the 
early  stages  of  the  development  of  the  individual.  Experi- 
ments are  being  conducted  on  an  extended  scale  in  endowed 
institutions.  There  is  notably  in  this  country,  established 
under  the  Carnegie  Institution,  a  station  for  experimental 
evolution,  at  Cold  Spring  Harbor,  New  York,  of  which  C.  B. 
Davenport  is  director.  Other  experimental  stations  in  Eng- 
land and  on  the  Continent  have  been  established,  and  we 
are  to  expect  as  the  result  of  coordinated  and  continuous 
experimental  work  many  substantial  contributions  to  the 
knowledge  of  inheritance. 


CHAPTER  XV 
THE  SCIENCE  OF  FOSSIL  REMAINS 

It  gradually  dawned  on  the  minds  of  men  that  the  crust 
of  the  earth  is  hke  a  gigantic  mausoleum,  containing  within  it 
the  remains  of  numerous  and  varied  forms  of  life  that  for- 
merly existed  upon  the  surface  of  the  earth.  The  evidence 
is  clear  that  untold  generations  of  hving  forms,  now  pre- 
served as  fossils,  inhabited  the  earth,  disported  themselves, 
and  passed  away  long  before  the  advent  of  man.  The  knowl- 
edge of  this  fossil  life,  on  account  of  its  great  diversity,  is 
an  essential  part  of  biology,  and  all  the  more  so  from  the 
circumstance  that  many  forms  of  life,  remains  of  which 
are  exhibited  in  the  rocks,  have  long  since  become  extinct. 
No  history  of  biology  would  be  complete  without  an  account 
of  the  rise  and  progress  of  that  department  of  biology  which 
deals  w^ith  fossil  remains. 

It  has  been  determined  by  collecting  and  systematically 
studying  the  remains  of  this  ancient  life  that  they  bear  testi- 
mony to  a  long,  unbroken  history  in  which  the  forms  of  both 
animals  and  plants  have  been  greatly  altered.  The  more 
ancient  remains  are  simple  in  structure,  and  form  with  the 
later  ones,  a  series  that  exhibits  a  gradually  increasing  com- 
plexity of  structure.  The  study  of  the  fossil  series  has 
brought  about  a  very  great  extension  of  our  knowledge 
regarding  the  age  of  the  world  and  of  the  conditions  under 
which  life  was  evolved. 

Strange  Views  Regarding  Fossils. — But  this  state  of  our 
knowledge  was  a  long  time  coming,  and  in  the  development 

322 


SCIENXE   OF   FOSSIL   REMAINS  323 

of  the  subject  we  can  recognize  several  distinct  epochs,  ''well- 
marked  by  prominent  features,  but  like  all  stages  of  intellec- 
tual growth,  without  definite  boundaries."  Fossils  were 
known  to  the  ancients,  and  by  some  of  the  foremost  philos- 
ophers of  Greece  were  understood  to  be  the  remains  of 
animals  and  plants.  After  the  revival  of  learning,  however, 
lively  controversies  arose  as  to  their  nature  and  their  meaning. 

Some  of  the  fantastic  ideas  that  were  entertained  regarding 
the  nature  of  fossil  remains  may  be  indicated.  The  fossils 
were  declared  by  many  to  be  freaks  of  nature;  others  main- 
tained that  they  were  the  results  of  spontaneous  generation, 
and  were  produced  by  the  plastic  forces  of  nature  within  the 
rocks  in  which  they  were  found  embedded.  Another  opinion 
expressed  was  that  they  were  generated  by  fermentations. 
As  the  history  of  intellectual  development  shows,  the  mind 
has  ever  seemed  benumbed  in  the  face  of  phenomena  that 
are  completely  misconceived ;  mystical  explanations  have  ac- 
cordingly been  devised  to  account  for  them.  Some  of  the 
pious  persons  of  that  period  declared  that  fossils  had  been 
made  and  distributed  by  the  Creator  in  pursuance  of  a  plan 
beyond  our  comprehension.  Another  droll  opinion  expressed 
was  that  the  Creator  in  His  wisdom  had  introduced  fossil 
forms  into  the  rocks  in  order  that  they  should  be  a  source  of 
confusion  to  the  race  of  geologists  that  was  later  to  arise. 

And  still  another  fantastic  conception  suggested  that  the 
fossils  were  the  original  molds  used  by  the  Creator  in  form- 
ing different  varieties  of  animals  and  plants,  some  of  which 
had  been  used  and  others  discarded.  It  was  supposed  that 
in  preparing  for  the  creation  of  life  He  experimented  and 
discarded  some  of  His  earliest  attempts;  and  that  fossils 
represented  these  discarded  molds  and  also,  perhaps,  some 
that  had  been  used  in  fashioning  the  created  forms. 

When  large  bones,  as  of  fossil  elephants,  began  to  be 
exhumed,  they  became  for  the  most  part  the  objects  of  stupid 


324  BIOLOGY    AND    ITS    MAKERS 

wonder.  The  passage  in  the  Scriptures  was  pointed  out, 
that  "there  were  giants  in  those  days,"  and  the  bones  were 
taken  to  be  evidences  of  the  former  existence  of  giants.  The 
opinions  expressed  regarding  the  fossil  bones  were  varied  and 
fantastic,  "some  saying  that  they  were  rained  from  Heaven, 
others  saying  that  they  were  the  gigantic  Hmbs  of  the  ancient 
patriarchs,  men  who  were  beHeved  to  be  tall  because  they 
were  known  to  be  old."  Following  out  this  idea,  "Henrion 
in  17 18  published  a  work  in  which  he  assigned  to  Adam  a 
height  of  123  feet  9  inches,  Noah  being  20  feet  shorter,  and 
so  on." 

Determination  of  the  Nature  of  Fossils.— In  due  course 
it  came  to  be  recognized  that  fossils  were  the  remains  of  forms 
that  had  been  alive  during  earlier  periods  of  time;  but  in 
reaching  this  position  there  was  continual  controversy.  Ob- 
jections were  especially  vigorous  from  theological  quarters, 
since  such  a  conclusion  was  deemed  to  be  contradictory  to 
the  Scriptures.  The  true  nature  of  fossils  had  been  clearly 
perceived  by  Leonardo  da  Vinci  (1452-15 19)  and  certain 
others  in  the  sixteenth  century. 

The  work,  however,  that  approached  more  nearly  to  sci- 
entific demonstration  was  that  of  Steno  (163 8- 1686),  a 
Dane  who  migrated  to  Italy  and  became  the  court  physician 
to  the  dukes  of  Tuscany.  He  was  a  versatile  man  who  had 
laid  fast  hold  upon  the  new  learning  of  his  day.  Eminent 
as  anatomist,  physiologist,  and  physician,  with  his  ever 
active  mind  he  undertook  to  encompass  all  learning.  It  is 
interesting  that  Steno — or  Stensen — after  being  passionately 
devoted  to  science,  became  equally  devoted  to  religion  and 
theology,  and,  forsaking  all  scientific  pursuits,  took  orders 
and  returned  to  his  native  country  with  the  title  of  bishop. 
Here  he  worked  in  the  service  of  humanity  and  religion  to 
the  end  of  his  life. 

In   reference   to  his  work   in   geology,  his  conclusions 


SCIENCE   OF   FOSSIL   REMAINS  325 

regarding  fossils  (1669)  were  based  on  the  dissection  of  the 
head  of  a  shark,  by  which  means  he  showed  an  almost  exact 
correspondence  between  certain  glossy  fossils  and  the  teeth 
of  living  sharks.  He  applied  his  reasoning,  that  like  effects 
imply  Hke  causes,  to  all  manner  of  fossils,  and  clearly  estab- 
lished the  point  that  they  should  be  regarded  as  the  remains 
of  animals  and  plants.  The  method  of  investigation  prac- 
ticed by  Steno  was  that  ''which  has  consciously  or  uncon- 
sciously guided  the  researches  of  palaeontologists  ever  since." 

Although  his  conclusions  were  well  supported,  they  did  not 
completely  overthrow  the  opposing  views,  and  become  a  fixed 
basis  in  geology.  When,  at  the  close  of  the  eighteenth  cen- 
tury and  the  beginning  of  the  nineteenth,  fossil  remains  were 
being  exhumed  in  great  quantities  in  the  Paris  basin,  Cuvier, 
the  great  French  naturalist,  reestablished  the  doctrine  that 
fossils  are  the  remains  of  ancient  life.  An  account  of  this 
will  be  given  presently,  and  in  the  mean  time  we  shall  go  on 
with  the  consideration  of  a  question  raised  by  the  conclusions 
of  Steno. 

Fossil  Deposits  Ascribed  to  the  Flood. — After  it  began  to 
be  reluctantly  conceded  that  fossils  might  possibly  be  the 
remains  of  former  generations  of  animals  and  plants,  there 
followed  a  period  characterized  by  the  general  belief  that  these 
entombed  forms  had  been  deposited  at  the  time  of  the 
Mosaic  deluge.  This  was  the  prevailing  view  in  the  eight- 
eenth century.  As  observ^ation  increased  and  the  extent  and 
variety  of  fossil  life  became  known,  as  well  as  the  positions 
in  which  fossils  were  found,  it  became  more  difficult  to  hold 
this  view  with  any  appearance  of  reason.  Large  forms  were 
found  on  the  tops  of  mountains,  and  also  lighter  forms  were 
found  near  the  bottom.  Miles  upon  miles  of  superimposed 
rocks  were  discovered,  all  of  them  bearing  quantities  of 
animal  forms,  and  the  interpretation  that  these  had  been 
killed  and  distributed  by  a  deluge  became  very  strained.     But 


326  BIOLOGY   AND    ITS   MAKERS 

to  the  reasoners  who  gave  free  play  to  their  fancies  the  facts 
of  observation  afforded  Httle  difficulty.  Some  declared  that 
the  entire  surface  of  the  earth  had  been  reduced  to  the  con- 
dition of  a  pasty  mass,  and  that  the  animals  drowned  by  the 
Deluge  had  been  deposited  within  this  pasty  mass  which, 
on  the  receding  of  the  waters,  hardened  into  rocks. 

The  belief  that  fossil  deposits  were  due  to  the  Deluge 
sensibly  declined,  however,  near  the  close  of  the  eighteenth 
century,  but  was  still  warmly  debated  in  the  earlv  part  of  the 
nineteenth  century.  Fossil  bones  of  large  tropical  animals 
having  been  discovered  about  1821,  embedded  in  the  stalag- 
mite-covered floor  of  a  cavern  in  Yorkshire,  England,  some 
of  the  ingenious  supporters  of  the  flood- theory  maintained 
that  caves  were  produced  by  gases  proceeding  from  the  bodies 
of  decaying  animals  of  large  size ;  that  they  were  like  large 
bubbles  in  the  crust  of  the  earth,  and,  furthermore,  that  bones 
found  in  caverns  were  either  those  from  the  decayed  carcasses 
or  others  that  had  been  deposited  during  the  occurrence  of 
the  Flood. 

Even  the  utterances  of  Cuvier,  in  his  theory  of  catastro- 
phism  to  which  we  shall  presently  return,  gave  countenance 
to  the  conclusion  that  the  Deluge  was  of  universal  extent. 
As  late  as  1823,  William  Buckland,  reader  in  geology  in 
Oxford,  and  later  canon  (1825)  of  Christ  Church,  and  dean 
(1845)  of  Westminster,  published  his  Reliquice  DiluviancB,  or 
Observations  on  the  Organic  Remains  Attesting  the  Action  of 
a  Universal  Deluge. 

The  theory  that  the  Mosaic  deluge  had  any  part  in  the 
deposit  of  organic  fossils  was  finally  surrendered  through  the 
advance  of  knowledge,  owing  mainly  to  the  labors  of  Lyell 
and  his  followers. 

The  Comparison  of  Fossil  and  Living  Animals. — The  very 
great  interest  connected  with  the  reestablishment  of  the  con- 
clusion of  Steno,  that  fossils  were  once  alive,  leads  us  to 


SCIENCE  OF  FOSSIL  REMAINS  327 

speak  more  at  length  of  the  discoveries  upon  which  Cuvier 
passed  his  opinion.  In  the  gypsum  rocks  about  Paris  the 
workmen  had  been  turning  up  to  the  Hght  bones  of  enormous 
size.  While  the  workmen  could  recognize  that  they  were 
bones  of  some  monsters,  they  were  entirely  at  loss  to  imagine 
to  what  kind  of  animals  they  had  belonged,  but  the  opinion 
was  frequently  expressed  that  they  were  the  bones  of  human 
giants. 

Cuvier,  with  his  extensive  preparation  in  comparative 
anatomy,  was  the  best  fitted  man  perhaps  in  all  the  world 
to  pass  judgment  upon  these  particular  bones.  He  went 
to  the  quarries  and,  after  observing  the  remains,  he  saw 
very  clearly  that  they  were  different  from  the  bones  of  any 
animals  now  existing.  His  great  knowledge  of  comparative 
anatomy  was  founded  on  a  comprehensive  study  of  the  bony 
system  as  well  as  the  other  structures  of  all  classes  of  living 
animals.  He  was  familiar  with  the  anatomy  of  elephants, 
and  when  he  examined  the  large  bones  brought  to  light  in  the 
quarries  of  Montmartre,  he  saw  that  he  was  confronted  with 
the  bones  of  elephant-like  animals,  but  animals  differing  in 
their  anatomy  from  those  at  present  living  on  the  earth. 

The  great  feature  of  Cuvier' s  investigations  was  that  he 
instituted  comparisons  on  a  broad  scale  between  fossil  re- 
mains and  living  animals.  It  was  not  merely  that  he  fol- 
lowed the  method  of  investigation  employed  by  Steno;  he 
went  much  further  and  reached  a  new  conclusion  of  great 
importance.  Not  only  was  the  nature  of  fossil  remains 
determined,  but  by  comparing  their  structure  with  that  of 
living  animals  the  astounding  inference  was  drawn  that  the 
fossil  remains  examined  belonged  to  forms  that  were  truly 
extinct.  This  discovery  marks  an  epoch  in  the  development 
of  the  knowledge  of  extinct  animals. 

Cuvier  the  Founder  of  Vertebrate  Palaeontology. — The 
interesting  discovery  that  the  fossil  relics  in  the  Eocene  rocks 


328  BIOLOGY   AND    ITS    MAKERS 

about  Paris  embraced  extinct  species  was  announced  to  the 
Institute  by  Cuvier  in  January,  1796;  and  thereafter  he  con- 
tinued for  a  quarter  of  a  century  to  devote  much  attention 
to  the  systematic  study  of  collections  made  in  that  district. 
These  observations  were,  however,  shared  with  other  labors 
upon  comparative  anatomy  and  zoology,  which  indicates  the 
prodigious  industry  for  which  he  was  notable.  In  181 2- 
1813  he  published  a  monumental  work,  profusely  illustrated, 
under  the  title  Ossemens  Fossiles.  This  standard  publication 
entitles  him  to  recognition  as  the  founder  of  vertebrate 
palaeontology. 

In  examining  the  records  of  fossil  life,  Cuvier  and  others 
saw  that  the  evidence  indicated  a  succession  of  animal  popu- 
lations that  had  become  extinct,  and  also  that  myriads  of  new 
forms  of  life  appeared  in  the  rocks  of  succeeding  ages.  Here 
Cuvier,  who  believed  that  species  were  fixed  and  unalterable, 
was  confronted  with  a  puzzling  problem.  In  attempting  to 
account  for  the  extinction  of  life,  and  what  seemed  to  him 
the  creation  of  new  forms,  he  could  see  no  way  out  consistent 
with  his  theoretical  views  except  to  assume  that  the  earth 
had  periodically  been  the  scene  of  great  catastrophes,  of 
which  the  Mosaic  deluge  was  the  most  recent,  but  possibly 
not  the  last.  He  supposed  that  these  cataclysms  of  nature 
resulted  in  the  extinction  of  all  life,  and  that  after  each  catas- 
trophe the  salubrious  condition  of  the  earth  was  restored, 
and  that  it  was  re- peopled  by  anew  creation  of  living  beings. 
This  conception,  known  as  the  theory  of  catastrophism, 
was  an  obstacle  to  the  progress  of  science.  It  is  to  be  re- 
gretted that  Cuvier  was  not  able  to  accept  the  views  of  his 
illustrious  contemporary  Lamarck,  who  believed  that  the 
variations  in  fossil  hfe,  as  well  as  those  of  living  forms,  were 
owing  to  gradual  transformations. 

Lamarck  Founds  Invertebrate  Palaeontology. — The  credit 
of  founding  the  science  of  palaeontology  does  not  belong 


SCIENCE  OF  FOSSIL  REMAINS  329 

exclusively  to  Cuvier.  Associated  with  his  name  as  co- 
founders  are  those  of  Lamarck  and  William  Smith.  Lamarck, 
that  quiet,  forceful  thinker  who  for  so  many  years  worked 
by*  the  side  of  Cuvier,  founded  the  science  of  invertebrate 
palaeontology.  The  large  bones  with  which  Cuvier  worked 
were  more  easy  to  be  recognized  as  unique  or  as  belonging 
to  extinct  animals  than  the  shells  which  occurred  in  abundance 
in  the  rocks  about  Paris.  The  latter  were  more  difficult  to 
place  in  their  true  position  because  the  number  of  forms 
of  Hfe  in  the  sea  is  very  extended  and  very  diverse.  Just  as 
Cuvier  was  a  complete  master  of  knowledge  regarding  verte- 
brate organization,  so  Lamarck  was  equally  a  master  of  that 
vast  domain  of  animal  forms  which  are  of  a  lower  grade 
of  organization — the  invertebrates.  From  his  study  of  the 
collections  of  shells  and  other  invertebrate  forms  from  the 
rocks,  Lamarck  created  invertebrate  palaeontology  and  this, 
coupled  with  the  work  of  Cuvier,  formed  the  foundations  of 
the  entire  field. 

Lamarck's  study  of  the  extinct  invertebrates  led  him  to 
conclusions  widely  at  variance  with  those  of  Cuvier.  Instead 
of  thinking  of  a  series  of  catastrophes,  he  saw  that  not  all  of 
the  forms  of  life  belonging  to  one  geological  period  became 
extinct,  but  that  some  of  them  were  continued  into  the  suc- 
ceeding period.  He  saw,  therefore,  that  the  succession  of 
life  in  the  rocks  bore  testimony  to  a  long  series  of  gradual 
changes  upon  the  earth's  surface,  and  did  not  in  any  way 
indicate  the  occurrence  of  catastrophes.  The  changes,  ac- 
cording to  the  views  of  Lamarck,  were  all  knit  together  into 
a  continuous  process,  and  his  conception  of  the  origin  of  life 
upon  the  earth  grew  and  expanded  until  it  culminated  in  the 
elaboration  of  the  first  consistent  theory  of  evolution. 

These  two  men,  Lamarck  and  Cuvier,  form  a  contrast 
as  to  the  favors  distributed  by  fortune:  Cuvier,  picturesque, 
highly  honored,  the  favorite  of  princes,  advanced  to  the 


330  BIOLOGY   AND    ITS    MAKERS 

highest  places  of  recognition  in  the  government,  acclaimed 
as  the  Jove  of  natural  science;  Lamarck,  hard-working,  ha- 
rassed by  poverty,  insufficiently  recognized,  and,  although 
more  gifted  than  his  confrere,  overlooked  by  the  scientific 
men  of  the  time.  The  judgment  of  the  relative  position  of 
these  two  men  in  natural  science  is  now  being  reversed,  and 
on  the  basis  of  intellectual  supremacy  Lamarck  is  coming 
into  general  recognition  as  the  better  man  of  the  two.  In 
the  chapters  dealing  with  organic  evolution  some  events  in 
the  life  of  this  remarkable  man  will  be  given. 

The  Arrangement  of  Fossils  in  Strata. — The  other  name 
associated  with  Lamarck  and  Cuvier  is  that  of  William  Smith, 
the  English  surveyor.  Both  Lamarck  and  Cuvier  were  men 
of  extended  scientific  training,  but  William  Smith  had  a 
moderate  education  as  a  surveyor.  While  the  two  former 
were  able  to  express  scientific  opinions  upon  the  nature  of 
the  fossil  forms  discovered,  William  Smith  went  at  his  task 
as  an  observer  with  a  clear  and  unprejudiced  mind,  an 
observer  who  walked  about  over  the  fields,  noticing  the  con- 
ditions of  rocks  and  of  fossil  forms  embedded  therein.  He 
noted  that  the  organic  remains  were  distributed  in  strata, 
and  that  particular  forms  of  fossil  life  characterized  par- 
ticular strata  and  occupied  the  same  relative  position  to  one 
another.  He  found,  for  illustration,  that  certain  particular 
forms  would  be  found  underlying  certain  other  forms  in  one 
mass  of  rocks  in  a  certain  part  of  the  country.  Wherever 
he  traveled,  and  whatever  rocks  he  examined,  he  found  these 
forms  occupying  the  same  relative  positions,  and  thus  he 
came  to  the  conclusion  that  the  living  forms  within  the  rocks 
constitute  a  stratified  series,  having  definite  and  imvarying 
arrangement  with  reference  to  one  another. 

In  short,  the  work  of  these  three  men — Cuvier,  Lamarck, 
and  William  Smith — placed  the  new  science  of  palaeontology 
upon  a  secure  basis  at  the  beginning  of  the  nineteenth  century. 


SCIENCE  OF  FOSSIL  REMAINS  331 

Summary. — The  chief  Steps  up  to  this  time  in  the  growth 
of  the  science  of  fossil  remains  may  now  be  set  forth  in  cate- 
gories, though  we  must  remember  that  the  advances  pro- 
ceeded concurrently  and  were  much  intermingled,  so  that, 
whatever  arrangement  we  may  adopt,  it  does  not  represent 
a  strict  chronological  order  of  events: 

I.  The  determination  of  the  nature  of  fossils.  Owing  to 
the  labors  of  Da  Vinci,  Steno,  and  Cuvier,  the  truth  was  estab- 
lished that  fossils  are  the  remains  of  former  generations  of 
animals  and  plants. 

II.  The  comparison  of  organic  fossils  with  living  forms 
that  was  instituted  on  a  broad  scale  by  Cuvier  resulted  in  the 
conclusion  that  some  of  the  fossils  belong  to  extinct  races. 
The  behef  of  Cuvier  that  entire  populations  became  extinct 
simultaneously,  led  him  to  the  theory  of  catastrophism.  The 
observations  of  Lamarck,  that,  while  some  species  disappear, 
others  are  continued  and  pass  through  transmutations,  were 
contrary  to  that  theory. 

III.  The  recognition  that  the  stratified  rocks  in  which 
fossils  are  distributed  are  sedimentary  deposits  of  gradual 
formation.  This  observation  and  the  following  took  the 
groimd  from  under  the  theory  that  fossils  had  been  deposited 
during  the  Mosaic  deluge. 

IV.  The  discovery  by  William  Smith  that  the  arrangement 
of  fossils  within  rocks  is  always  the  same,  and  the  relative 
age  of  rocks  may  be  determined  by  an  examination  of  their 
fossil  contents. 

Upon  the  basis  of  the  foregoing,  we  come  to  the  next 
advance,  viz.: 

V.  The  application  of  this  knowledge  to  the  determination 
of  the  history  of  the  earth. 

Fossil  Remains  as  an  Index  to  the  Past  History  of  the 
Earth. — The  most  advanced  and  enlightened  position  that 
had  been  taken  in  reference  to  the  fossil  series  during  the 


33^ 


BIOLOGY   AND    ITS    MAKERS 


first  third  of  the  nineteenth  century  was  that  taken  by 
Lamarck,  he  being  the  first  to  read  in  the  series  the  history 
of  Hfe  upon  the  globe,  weaving  it  into  a  connected  story,  and 
estabhshing  thereon  a  doctrine  of  organic  evolution.  It  was 
not  until  after  1859,  however,  that  the  truth  of  this  conclusion 
was  generally  admitted,  and  when  it  was  accepted  it  was  not 
through  the  earlier  publications  of  Lamarck,  but  through 
the  arguments  of  later  observers,  founded  primarily  upon 
the  hypothesis  set  forth  by  Darwin.  There  were  several 
gradations  of  scientific  opinion  in  the  period,  short  as  it 
was,  between  the  time  of  Cuvier  and  of  Darwin;  and  this 
intermediate  period  was  one  of  contention  and  warfare 
between  the  theologians  and  the  geologists.  Cuvier  had 
championed  the  theory  of  a  succession  of  catastrophes,  and 
since  this  hypothesis  did  not  come  into  such  marked  conflict 
with  the  prevailing  theological  opinion  as  did  the  views  of 
Lamarck,  the  theologians  were  ready  to  accept  the  notion  of 
Cuvier,  and  to  point  with  considerable  satisfaction  to  his 
unique  position  as  an  authority. 

Lyell. — In  1830  there  was  published  an  epoch-making 
work  in  geology  by  Charles  Lyell  (Fig.  97),  afterward 
Sir  Charles,  one  of  the  most  brilliant  geologists  of  all  the 
world.  This  British  leader  of  scientific  thought  showed  the 
prevalence  of  a  uniform  law  of  development  in  reference  to 
the  earth's  surface.  He  pointed  out  the  fact  that  had  been 
maintained  by  Hutton,  that  changes  in  the  past  were  to  be 
interpreted  in  the  light  of  what  is  occurring  in  the  present. 
By  making  a  careful  study  of  the  work  performed  by  the 
waters  in  cutting  down  the  continents  and  in  transferring  the 
eroded  material  to  other  places,  and  distributing  it  in  the  form 
of  deltas ;  by  observing  also  the  action  of  frost  and  wind  and 
wave;  by  noting,  furthermore,  the  conditions  under  which 
animals  die  and  are  subsequently  covered  up  in  the  matrix 
of  detritus — by  all  this  he  showed  evidences  of  a  series  of 


SCIENCE  OF  FOSSIL  REMAINS 


333 


slow,  continuous  changes  that  have  occurred  in  the  past  and 
have  molded  the  earth's  crust  into  its  present  condition. 

He  showed,  further,  that  organic  fossils  are  no  exception 
to  this  law  of  uniform  change.  He  pointed  to  the  evidences 
that  ages  of  time  had  been  required  for  the  formation  of  the 
rocks  bearing  fossils;  and  that  the  regular  succession  of  animal 


Fig.  97. — Charles  Lyell,   1797-1875. 

forms  indicates  a  continual  process  of  development  of  animal 
life ;  and  that  the  disappearance  of  some  forms,  that  is,  their 
becoming  extinct,  was  not  owing  to  sudden  changes,  but  to 
gradual  changes.  When  this  view  was  accepted,  it  overthrew 
the  theory  of  catastrophism  and  replaced  it  by  one  designated 
uniformatism,  based  on  the  prevalence  of  uniform  natural 
laws. 

This  new  conception,  with  all  of  its  logical  inferences, 


334  BIOLOGY   AND    ITS   MAKERS 

was  scouted  by  those  of  theological  bias,  but  it  won  its  way 
in  the  scientific  world  and  became  an  important  feature  in 
preparing  for  the  reception  of  Darwin's  great  book  upon  the 
descent  of  animal  Hfe. 

We  step  forward  now  to  the  year  1859,  to  consider  the 
effect  upon  the  science  of  palaeontology  of  the  publication  of 
Darwin's  Origin  of  Species.  Its  influence  was  tremend- 
ous. The  geological  theories  that  had  provoked  so  much 
controversy  were  concerned  not  merely  with  the  disappear- 
ance of  organic  forms,  but  also  with  the  introduction  of  new 
species.  The  Origin  of  Species  made  it  clear  that  the  only 
rational  point  of  view  in  reference  to  fossil  life  was  that  it 
had  been  gradually  developed,  that  it  gave  us  a  picture  of 
the  conditions  of  life  upon  the  globe  in  past  ages,  that  the 
succession  of  forms  within  the  rocks  represented  in  outline 
the  successive  steps  in  the  formation  of  different  kinds  of 
animals  and  plants. 

Owen. — Both  before  and  after  Darwin's  hypothesis  was 
given  to  science,  notable  anatomists,  a  few  of  whom  must  be 
mentioned,  gave  attention  to  fossil  remains.  Richard  Owen 
(1804-1892)  had  his  interest  in  fossil  hfe  stimulated  by  a 
visit  to  Cuvier  in  1831,  and  for  more  than  forty  years  there- 
after he  published  studies  on  the  structure  of  fossil  animals. 
His  studies  on  the  fossil  remains  of  Australia  and  New 
Zealand  brought  to  light  some  interesting  forms.  The  ex- 
tinct giant  bird  of  New  Zealand  (Fig.  98)  was  a  spectacular 
demonstration  of  the  enormous  size  to  which  birds  had 
attained  during  the  Eocene  period.  Owen's  monograph 
(1879)  on  the  oldest  known  bird — the  archaeopteryx — de- 
scribed an  interesting  form  uniting  both  bird-like  and  rep- 
tilian characteristics. 

Agassiz. — Louis  Agassiz  (1807-1873)  (Fig.  99)  also  came 
into  close  personal  contact  with  Cuvier,  and  produced  his 
first  great  work  partly  under  the  stimulus  of  the  latter.    When 


I 


Fig.  98. — Professor  Owen  and  the  Extinct  Fossil  Bird  (Dinornis) 
of  New  Zealand. 
Permission  of  D.  Appleton  &  Co. 


33^ 


BIOLOGY   AND    ITS    MAKERS 


Agassiz  visited  Paris,  Cuvier  placed  his  collections  at  Agassiz's 
disposal,  together  with  numerous  drawings  of  fossil  fishes. 
The  profusely  illustrated  monograph  of  Agassiz  on  the  fossil 
fishes  (i  833-1 844)   began  to  appear  in  1833,  the  year  after 


Fig.  99. — Louis  Agassiz,   1807-1873. 


Cuvier' s  death,  and  was  carried  on  eleven  years  before  it  was 
completed. 

Agassiz,  with  his  extensive  knowledge  of  the  developmen- 
tal stages  of  animals,  came  to  see  a  marked  parallelism 
between  the  stages  in*  development  of  the  embryo  and  the 
successive  forms  in  the  geological  series.  This  remarkable 
parallelism  between  the  fossil  forms  of  life  and  the  stages 


SCIENCE  OF  FOSSIL  REMAINS  337 

in  the  development  of  higher  forms  of  recent  animals  is 
very  interesting  and  very  significant,  and  helps  materially 
in  elucidating  the  idea  that  the  fossil  series  represent  roughly 
the  successive  stages  through  which  animal  forms  have 
passed  in  their  upward  course  of  development  from  the 
simplest  to  the  highest,  through  long  ages  of  time.  Curi- 
ously enough,  however,  Agassiz  failed  to  grasp  the  meaning 
of  the  principle  that  he  had  worked  out.  After  illustrating 
so  nicely  the  process  of  organic  evolution,  he  remained  !to  the 
end  of  his  life  an  opponent  of  that  theory.  i 

Huxley. — Thomas  Henry  Huxley  (1825-1895)  wals  led 
to  study  fossil  life  on  an  extended  scale,  and  he  shed  light  in 
this  province  as  in  others  upon  which  he  touched.  Wit)i  crit- 
ical analysis  and  impartial  mind  he  applied  the  principles 
of  evolution  to  the  study  of  fossil  remains.  His  first  conclu- 
sion was  that  the  evidence  of  evolution  derived  from  palaeon- 
tology was  negative,  but  with  the  advances  in  discovery  he 
grew  gradually  to  recognize  that  palaeontologists,  in  bringing 
to  light  complete  evolutionary  series,  had  supplied  some  of 
the  strongest  supporting  evidence  of  organic  evolution.  By 
many  geologists  fossils  have  been  used  as  time-markers  for 
the  determination  of  the  age  of  various  deposits;  but,  with 
Huxley,  the  study  of  them  was  always  biological.  It  is  to 
the  latter  point  of  view  that  palaeontology  owes  its  great 
importance  and  its  great  development.  The  statement  of 
Huxley,  that  the  only  difference  between  a  fossil  and  a  recent 
animal  is  that  one  has  been  dead  longer  than  the  other, 
represents  the  spirit  in  which  the  study  is  being  carried 
forward. 

With  the  establishment  of  the  doctrine  of  organic  evolu- 
tion palaeontology  entered  upon  its  modem  phase  of  growth; 
upon  this  basis  there  is  being  reared  a  worthy  structure 
through  the  efforts  of  the  recent  votaries  to  the  science.  It 
is  neither  essential  nor  desirable  that  the  present  history  of 


33^ 


BIOLOGY   AND    ITS    MAKERS 


the  subject  should  be  followed  here  in  detail.  The  collec- 
tions of  material  upon  which  palaeontologists  are  working 
have  been  enormously  increased,  and  there  is  perhaps  no 
place  where  activity  has  been  greater  than  in  the  United 
States.     The   rocks  of  the  Western  States  and   Territories 


Fig. 


-E.  D.  Cope,   1840-1897. 


embrace  a  very  rich  collection  of  fossil  forms,  and,  through 
the  generosity  of  several  wealthy  men,  exploring  parties  have 
been  provided  for  and  immense  collections  have  been  brought 
back  to  be  preserved  in  the  museums,  especially  of  New 
Haven,  Conn.,  and  in  the  American  Museum  of  Natural  His- 
tory in  New  York  City. 


SCIENCE  OF  FOSSIL  REMAINS  339 

Leidy,  Cope,  and  Marsh.— Among  the  early  explorers  of 
the  fossils  of  the  West  must  be  named  Joseph  Leidy,  E.  D. 
Cope  (Fig.  100),  and  O.  C.  Marsh.  These  gentlemen  all 
had  access  to  rich  material,  and  all  of  them  made  notable 
contributions  to  the  science  of  palaeontology.     The  work  of 


Fig.   ioi. — O.  C.  Marsh,   1831-1899. 

Cope  (i  840-1 897)  is  very  noteworthy.  He  was  a  compar- 
ative anatomist  equal  to  Cuvier  in  the  extent  of  his  knowl- 
edge, and  of  larger  philosophical  views.  His  extended  publi- 
cations under  the  direction  of  the  United  States  Government 
have  very  greatly  extended  the  knowledge  of  fossil  vertebrate 
life  in  America. 


340  BIOLOGY   AND    ITS   MAKERS 

O.  C.  Marsh  (Fig.  loi)  is  noteworthy  for  similar  explora- 
tions; his  discovery  of  toothed  birds  in  the  Western  rocks 
and  his  collection  of  fossil  horses,  until  recently  the  most  com- 
plete one  in  existence,  are  all  very  well  known.  Throughout 
his  long  life  he  contributed  from  his  own  private  fortune,  and 
intellectually  through  his  indefatigable  labors,  to  the  progress 
of  palaeontology. 

Zittel. — The  name  most  widely  known  in  palaeontology 
is  that  of  the  late  Karl  von  Zittel  (1839- 1904),  who  devoted 
all  his  working  hfe  to  the  advancement  of  the  science  of  fos- 
sils. :  In  his  great  work,  Handhuch  der  Palaeontologie  (1876- 
1893),  he  brought  under  one  view  the  entire  range  of  fossils 
from  the  protozoa  up  to  the  mammals.  Osbom  says:  ''It 
is  probably  not  an  exaggeration  to  say  that  he  did  more  for 
the  promotion  and  diffusion  of  palaeontology  than  any  other 
single  man  who  lived  during  the  nineteenth  century.  While 
not  gifted  with  genius,  he  possessed  extraordinary  judg- 
ment, critical  capacity,  and  untiring  industry."  His  portrait 
(Fig.!  iv02)  shows  a  face  "full  of  keen  intelligence  and  enthu- 
siasn^." 

Zjittel's  influence  was  exerted  not  only  through  his  writ- 
ings,* but  also  through  his  lectures  and  the  stimulus  imparted 
to  the  large  number  of  young  men  who  were  attracted  to 
Munich  to  study  under  his  direction.  These  disciples  are 
now  j  distributed  in  various  universities  in  Europe  and  the 
United  States,  and  are  there  carrying  forward  the  work  begun 
by  Zittel.  The  great  collection  of  fossils  which  he  left  at 
Munich  contains  illustrations  of  the  whole  story  of  the  evolu- 
tion of  life  through  geological  ages. 

Recent  Developments. — The  greatest  advance  now  being 
made  in  the  study  of  fossil  vertebrate  life  consists  in  establish- 
ing the  lineage  of  families,  orders,  and  classes.  Investigators 
have  been  especially  fortunate  in  working  out  the  direct  line 
of  descent  of  a  number  of  living  mammals.     Fossils  have 


SCIENCE   OF   FOSSIL   REMAINS 


341 


been  collected  which  supply  a  panoramic  view  of  the  line  of 
descent  of  horses,  of  camels,  of  rhinoceroses,  and  of  other 
animals.  The  most  fruitful  worker  in  this  field  at  the  present 
time  is  perhaps  Henry  F.  Osborn,  of  the  American  Museum 


i^^^^^^^^^^^l 

IL5 

K 
m 

iF 

■1'..  '.■■■.K;':- 

5* 

1 

Fig.   102. — Karl  von  Zittel,   1839-1904. 


of  Natural  History,  New  York  City.  His  profound  and 
important  investigations  in  the  ancestry  of  animal  life  are 
now  nearing  the  time  of  their  publication  in  elaborated 
form. 


342  BIOLOGY   AND    ITS    MAKERS 

Palaeontology,  by  treating  fossil  life  and  recent  life  in  the 
same  category,  has  come  to  be  one  of  the  important  lines  of 
investigation  in  biology.  It  is,  of  course,  especially  rich  in 
giving  us  a  knowledge  of  the  hard  parts  of  animals,  but  by 
ingenious  methods  we  can  arrive  at  an  idea  of  some  of  the 
soft  parts  that  have  completely  disappeared.  Molds  of  the 
interior  of  the  cranium  can  be  made,  and  thus  one  may  form 
a  notion  of  the  relative  size  and  development  of  the  brain 
in  different  vertebrated  animals.  This  method  of  making 
molds  and  studying  them  has  shown  that  one  characteristic 
of  the  geological  time  of  the  tertiary  period  was  a  marked 
development  in  regard  to  the  brain  size  of  the  different 
animals.  There  was  apparently,  just  prior  to  the  quaternary 
epoch,  a  need  on  the  part  of  animals  to  have  an  increased 
brain-growth;  and  one  can  not  doubt  that  this  feature  which 
is  demonstrated  by  fossil  life  had  a  great  influence  in  the 
development  of  higher  animal  forms. 

The  methods  of  collecting  fossils  in  the  field  have  been 
greatly  developed.  By  means  of  spreading  mucilage  and 
tissue  paper  over  delicate  bones  that  crumble  on  exposure 
to  the  air,  and  of  wrapping  fossils  in  plaster  casts  for  trans- 
portation, it  has  been  made  possible  to  uncover  and  preserve 
many  structures  which  with  a  rougher  method  of  handling 
would  have  been  lost  to  science. 

Fossil  Man. — One  extremely  interesting  section  of  palae- 
ontology deals  with  the  fossil  remains  of  the  supposed 
ancestors  of  the  present  human  race.  Geological  evidence 
establishes  the  great  antiquity  of  man,  but  up  to  the  present 
time  little  systematic  exploration  has  been  carried  on  with 
a  view  to  discover  all  possible  traces  of  fossil  man.  From 
time  to  time  since  1840  there  have  been  discovered  in  caverns 
and  river- gravels  bones  which,  taken  together,  constitute  an 
interesting  series.  The  parts  of  the  skull  are  of  especial 
importance  in  this  kind  of  study,  and  there  now  exists  in 


SCIENCE  OF  FOSSIL  REMAINS  343 

different  collections  a  series  containing  the  Neanderthal 
skull,  the  skulls  of  Spy  and  Engis,  and  the  Java  skull  de- 
scribed in  1894  by  Dubois.  There  have  also  been  found 
recently  (November,  1906)  in  deposits  near  Lincohi,  Neb., 
some  fossil  human  remains  that  occupy  an  intermediate 
position  between  the  Neanderthal  skull  and  the  skulls  of  the 
lower  representatives  of  living  races  of  mankind.  We  shall 
have  occasion  to  revert  to  this  question  in  considering  the 
evidences  of  organic  evolution.     (See  page  364.) 

The  name  palaeontology  was  brought  into  use  about  1830. 
The  science  affords,  in  some  particulars,  the  most  interesting 
field  for  biological  research,  and  the  feature  of  the  recon- 
struction of  ancient  life  and  the  determination  of  the  lineage 
of  living  forms  has  taken  a  strong  hold  on  the  popular  imag- 
ination. According  to  O shorn,  the  most  important  palaeon- 
tological  event  of  recent  times  was  the  discovery,  in  1900,  of 
fossil  beds  of  mammals  in  the  Faylim  lake-province  of  Egypt, 
about  forty-seven  miles  south  of  Cairo.  Here  are  embedded 
fossil  forms,  some  of  which  have  been  already  described  in  a 
volume  by  Charles  W.  Andrews,  which  Osbom  says  ''marks 
a  turning-point  in  the  history  of  mammalia  of  the  world." 
It  is  now  estabHshed  that  "Africa  was  a  very  important  center 
in  the  evolution  of  mammalian  life."  It  is  expected  that  the 
lineage  of  several  orders  of  mammalia  will  be  cleared  up 
through  the  further  study  of  fossils  from  this  district. 


PART  II 

THE  DOCTRINE  OF  ORGANIC 
EVOLUTION 


CHAPTER  XVI 

WHAT  EVOLUTION  IS:    THE  EVIDENCE  UPON 
WHICH    IT   RESTS,  ETC. 

The  preceding  pages  have  been  devoted  mainly  to  an 
account  of  the  shaping  of  ideas  in  reference  to  the  architec- 
ture, the  physiolog}^,  and  the  development  of  animal  life. 

We  come  now  to  consider  a  central  theme  into  which  all 
these  ideas  have  been  merged  in  a  unified  system;  viz.,  the 
process  by  which  the  diverse  forms  of  animals  and  plants 
have  been  produced. 

Crude  speculations  regarding  the  derivation  of  living 
forms  are  very  ancient,  and  we  may  say  that  the  doctrine  of 
organic  evolution  was  foreshadowed  in  Greek  thought.  The 
serious  discussion  of  the  question,  however,  was  reserved 
for  the  nineteenth  century.  The  earlier  naturalists  accepted 
animated  nature  as  they  found  it,  and  for  a  long  time  were 
engaged  in  becoming  acquainted  merely,  with  the  different 
kinds  of  animals  and  plants,  in  working  out  their  anatomy 
and  development;  but  after  some  progress  had  been  made 
in  this  direction  there  came  swinging  into  their  horizon 
deeper  questions,  such  as  that  of  the  derivation  of  living 
forms.  The  idea  that  the  higher  forms  of  life  are  de- 
rived from  simpler  ones  by  a  process  of  gradual  evolution 
received  general  acceptance,  as  we  have  said  before,  only 
in  the  last  part  of  the  nineteenth  century,  after  the  work  of 
Charles  Darwin;  but  we  shall  presently  see  how  the  theory 
of  organic  development  was  thought  out  in  completeness  by 

347 


348  BIOLOGY   AND    ITS   MAKERS 

Lamarck  in  the  last  years  of  the  eighteenth  century,  and  was 
further  molded  by  others  before  Darwin  touched  it. 

Vagueness  Regarding  Evolution. — Although ''evolution" 
is  to-day  a  word  in  constant  use,  there  is  still  great  vagueness 
in  the  minds  of  most  people  as  to  what  it  stands  for;  and, 
what  is  more,  there  is  very  little  general  information  dissem- 
inated regarding  the  evidence  by  which  it  is  supported,  and  re- 
garding the  present  status  of  the  doctrine  in  the  scientific  world. 

In  its  broad  sense,  evolution  has  come  to  mean  the  devel- 
opment of  all  nature  from  the  past.  We  may,  if  we  wish, 
think  of  the  long  train  of  events  in  the  formation  of  the  world, 
and  in  supplying  it  with  life  as  a  story  inscribed  upon  a  scroll 
that  is  being  gradually  unrolled.  Everything  which  has 
come  to  pass  is  on  that  part  so  far  exposed,  and  everything 
in  the  future  is  still  covered,  but  will  appear  in  due  course 
of  time;  thus  the  designation  of  evolution  as  ''the  unrolling 
of  the  scroll  of  the  universe"  becomes  picturesquely  sug- 
gestive. In  its  wide  meaning,  it  includes  the  formation  of 
the  stars,  solar  systems,  the  elements  of  the  inorganic  world, 
as  well  as  all  living  nature — this  is  general  evolution;  but 
the  word  as  commonly  employed  is  limited  to  organic  evolu- 
tion, or  the  formation  of  life  upon  our  planet.  It  will  be 
used  hereafter  in  this  restricted  sense. 

The  vagueness  regarding  the  theory  of  organic  evolution 
arises  chiefly  from  not  understanding  the  points  at  issue. 
One  of  the  commonest  mistakes  is  to  confuse  Darwinism 
with  organic  evolution.  It  is  known,  for  illustration,  that  con- 
troversies are  current  among  scientific  workers  regarding 
Darwinism  and  certain  phases  of  evolution,  and  from  this 
circumstance  it  is  assumed  that  the  doctrine  of  organic 
evolution  as  a  whole  is  losing  ground.  The  discussions  of  De 
Vries  and  others — all  believers  in  organic  evolution — at  the 
Scientific  Congress  in  St.  Louis  in  1904,  led  to  the  statement 
in  the  public  press  that  the  scientific  world  was  haggling 


ORGANIC   EVOLUTION  349 

over  the  evolution-theory,  and  that  it  was  beginning  to  sur- 
render it.  Such  statements  are  misleading  and  tend  to  per- 
petuate the  confusion  regarding  the  present  status  of  the 
evolution  theory.  Never  before  was  the  doctrine  of  organic 
evolution  so  thoroughly  entrenched  in  the  mind  of  the 
scientific  world. 

The  theory  of  organic  evolution  relates  to  the  history  of 
animal  and  plant  hfe,  while  Darwin's  theory  of  natural  selec- 
tion is  only  one  of  the  various  attempts  to  point  out  the 
causes  for  that  history's  being  what  it  is.  An  attack  upon 
Darwinism  is  not,  in  itself,  an  attack  upon  the  general  the- 
ory, but  upon  the  adequacy  of  his  explanation  of  the  way 
in  which  nature  has  brought  about  the  diversity  of  animal 
and  plant  life.  Natural  selection  is  the  particular  factor 
which  Darwin  has  emphasized,  and  the  discussion  of  the 
part  played  by  other  factors  tends  only  to  extend  the  knowl- 
edge of  the  evolutionary  process,  without  detracting  from  it 
as  a  general  theory. 

While  the  controversies  among  scientific  men  relate  for 
the  most  part  to  the  influences  that  have  been  operative  in 
bringing  about  organic  evolution,  nevertheless  there  are  a  few 
in  the  scientific  camp  who  repudiate  the  doctrine.  Fleisch- 
mann,  of  Erlangen,  is  perhaps  the  most  conspicuous  of  those 
who  are  directing  criticism  against  the  general  doctrine, 
maintaining  that  it  is  untenable.  Working  biologists  will  be 
the  first  to  admit  that  it  is  not  demonstrated  by  indubitable 
evidence,  but  the  weight  of  evidence  is  so  compelling  that 
scientific  men  as  a  body  regard  the  doctrine  of  organic  evolu- 
tion as  merely  expressing  a  fact  of  nature,  and  we  can  not 
in  truth  speak  of  any  considerable  opposition  to  it.  Since 
Fleischmann  speaks  as  an  anatomist,  his  suppression  of 
anatomical  facts  with  which  he  is  acquainted  and  his  form  of 
special  pleading  have  impressed  the  biological  world  as  lack- 
ing in  sincerity. 


3SO  BIOLOGY   AND    ITS    MAKERS 

This  is  not  the  place,  however,  to  deal  with  the  technical 
aspects  of  the  discussion  of  the  factors  of  organic  evolution; 
it  is  rather  our  purpose  here  to  give  a  descriptive  account  of 
the  theory  and  its  various  explanations.  First  we  should 
aim  to  arrive  at  a  clear  idea  of  what  the  doctrine  of  evolution 
is,  and  the  basis  upon  which  it  rests;  then  of  the  factors  which 
have  been  emphasized  in  attempted  explanations  of  it;  and, 
finally,  of  the  rise  of  evolutionary  thought,  especially  in  the 
nineteenth  century.  The  bringing  forward  of  these  points 
will  be  the  aim  of  the  following  pages. 

Nature  of  the  Question. — It  is  essential  at  the  outset  to 
perceive  the  nature  of  the  question  involved  in  the  theories 
of  organic  evolution.  It  is  not  a  metaphysical  question,  ca- 
pable of  solution  by  reflection  and  reasoning  with  symbols; 
the  data  for  it  must  rest  upon  observation  of  what  has  taken 
place  in  the  past  in  so  far  as  the  records  are  accessible.  It 
is  not  a  theological  question,  as  so  many  have  been  disposed 
to  argue,  depending  upon  theological  methods  of  interpreta- 
tion. It  is  not  a  question  of  creation  through  divine  agencies, 
or  of  non-creation,  but  a  question  of  method  of  creation. 

Evolution  as  used  in  biology  is  merely  a  history  of  the 
steps  by  which  animals  and  plants  came  to  be  what  they  are. 
It  is,  therefore,  a  historical  question,  and  must  be  investigated 
by  historical  methods.  Fragments  of  the  story  of  creation 
are  found  in  the  strata  of  the  earth's  crust  and  in  the  stages 
of  embryonic  development.  These  clues  must  be  brought 
together;  and  the  reconstruction  of  the  story  is  mainly  a 
matter  of  getting  at  the  records.  Drummond  says  that  evo- 
lution is  "the  story  of  creation  as  told  by  those  who  know 
it  best." 

The  Historical  Method. — The  historical  method  as  ap- 
plied to  searchhig  out  the  early  history  of  mankind  finds  a 
parallel  in  the  investigations  into  the  question  of  organic 
evolution.     In  the  buried  cities  of  Palestine  explorers  have 


ORGANIC   EVOLUTION  35^ 

uncovered  traces  of  ancient  races  and  have  in  a  measure 
reconstructed  their  history  from  fragments,  such  as  coins, 
various  objects  of  art  and  of  household  use,  together  with 
inscriptions  on  tom.bs  and  columns  and  on  those  curious  little 
bricks  which  were  used  for  public  records  and  correspond- 
ence. One  city  having  been  uncovered,  it  is  found  by  lifting 
the  floors  of  temples  and  other  buildings,  and  the  pavement 
of  public  squares,  that  this  city,  although  very  ancient,  is 
built  upon  the  ruins  of  a  more  ancient  one,  which  in  turn 
covers  the  ruins  of  one  still  older.  In  this  way,  as  many  as 
seven  successive  cities  have  been  found,  built  one  on  top  of 
the  other,  and  new  and  unexpected  facts  regarding  ancient 
civilization  have  been  brought  to  light.  We  must  admit  that 
this  gives  us  an  imperfect  history,  with  many  gaps;  but  it  is 
one  that  commands  our  confidence,  as  being  based  on  facts 
of  observation,  and  not  on  speculation. 

In  like  manner  the  knowledge  of  the  past  history  of  animal 
life  is  the  result  of  explorations  by  trained  scholars  into  the 
records  of  the  past.  We  have  remains  of  ancient  life  in  the 
rocks,  and  also  traces  of  past  conditions  in  the  developing 
stages  of  animals.  These  are  all  more  ancient  than  the 
inscriptions  left  by  the  hand  of  man  upon  his  tombs,  his 
temples,  and  his  columns,  but  nevertheless  full  of  meaning 
if  we  can  only  understand  them.  This  historical  method  of 
investigation  applied  to  the  organic  world  has  brought  new 
and  unexpected  views  regarding  the  antiquity  of  life. 

The  Diversity  of  Living  Forms. — Sooner  or  later  the 
question  of  the  derivation  of  the  animals  and  plants  is 
bound  to  come  to  the  mind  of  the  observer  of  nature.  There 
exist  at  present  more  than  a  million  different  kinds  of 
animals.  The  waters,  the  earth,  the  air  teem  with  life. 
The  fishes  of  the  sea  are  almost  innumerable,  and  in  a  sin- 
gle order  of  the  insect- world,  the  beetles,  more  than  50,000 
species  are  known  and  described.     In  addition  to   living 


352  BIOLOGY    AND    ITS    MAKERS 

animals,  there  is  entombed  in  the  rocks  a  great  multitude 
of  fossil  forms  which  lived  centuries  ago,  and  many  of  which 
have  become  entirely  extinct.  How  shall  this  great  diversity 
of  life  be  accounted  for?  Has  the  great  variety  of  forms 
existed  unchanged  from  the  days  of  their  creation  to  the 
present  ?  Or  have  they,  perchance,  undergone  modifications 
so  that  one  original  form,  or  at  least  a  few  original  types, 
may  have  through  transformations  merged  into  different 
kinds  ?  This  is  not  merely  an  idle  question,  insoluble  from 
the  very  nature  of  the  case;  for  the  present  races  of  animals 
have  a  lineage  reaching  far  into  the  past,  and  the  question 
of  fixity  of  form  as  against  alteration  of  type  is  a  historical 
question,  to  be  answered  by  getting  evidence  as  to  their  line 
of  descent. 

Are  Species  Fixed  in  Nature? — The  aspect  of  the  matter 
which  presses  first  upon  our  attention  is  this:  Are  the  species 
(or  different  kinds  of  animals  and  plants)  fixed,  and,  within 
narrow  limits,  permanent,  as  Linnaeus  supposed?  Have 
they  preserved  their  identity  through  all  time,  or  have  they 
undergone  changes  ?  This  is  the  heart  of  the  question  of 
organic  evolution.  If  observation  shows  species  to  be  con- 
stant at  the  present  time,  and  also  to  have  been  continuous 
so  far  as  we  can  trace  their  parentage,  we  must  conclude  that 
they  have  not  been  formed  by  evolution;  but  if  we  find 
evidence  of  their  transmutation  into  other  species,  then  there 
has  been  evolution. 

It  is  well  estabhshed  that  there  are  wide  ranges  of  varia- 
tion among  animals  and  plants,  both  in  a  wild  state  and  under 
domestication.  Great  changes  in  flowers  and  vegetables  are 
brought  about  through  cultivation,  while  breeders  produce 
different  kinds  of  pigeons,  fowls,  and  stock.  We  know, 
therefore,  that  living  beings  may  change  through  modification 
of  the  circumstances  and  conditions  that  affect  their  lives. 
But  general  observations  extending  over  a  few  decades  are 


ORGANIC   EVOLUTION  353 

not  sufficient.  We  must,  if  possible,  bring  the  history  of 
past  ages  to  bear  upon  the  matter,  and  determine  whether  or 
not  there  had  been,  with  the  lapse  of  time,  any  considerable 
alteration  in  living  forms. 

Evolutionary  Series. — Fortunately,  there  are  preserved 
in  the  rocks  the  petrified  remains  of  animals,  showing  their 
history  for  many  thousands  of  years,  and  we  may  use  them 
to  test  the  question.  It  is  plain  that  rocks  of  a  lower  level 
were  deposited  before  those  that  cover  them,  and  we  may 
safely  assume  that  the  fossils  have  been  preserved  in  their 
proper  chronological  order.  Now,  we  have  in  Slavonia  some 
fresh-water  lakes  that  have  been  drying  up  from  the  tertiary 
period.  Throughout  the  ages,  these  waters  were  inhabited 
by  snails,  and  naturally  the  more  ancient  ones  were  the  par- 
ents of  the  later  broods.  As  the  animals  died  their  shells 
sank  to  the  bottom  and  were  covered  by  mud  and  debris, 
and  held  there  like  currants  in  a  pudding.  In  the  course  of 
ages,  by  successive  accumulations,  these  layers  thickened 
and  were  changed  into  rock,  and  by  this  means  shells  have 
been  preserved  in  their  proper  order  of  birth  and  life,  the  most 
ancient  at  the  bottom  and  the  newest  at  the  top.  We  can 
sink  a  shaft  or  dig  a  trench,  and  collect  the  shells  and  arrange 
them  in  proper  order. 

Although  the  shells  in  the  upper  strata  are  descended  from 
those  near  the  bottom,  they  are  very  different  in  appearance. 
No  one  would  hesitate  to  name  them  different  species;  in 
fact,  when  collections  were  first  made,  naturalists  classified 
these  shells  into  six  or  eight  different  species.  If,  however,  a 
collection  embracing  shells  from  all  levels  is  arranged  in  a 
long  row  in  proper  order,  a  different  light  is  thrown  on  the 
matter;  while  those  at  the  ends  are  unlike,  yet  if  we  begin 
at  one  end  and  pass  to  the  other  we  observe  that  the  shells 
all  grade  into  one  another  by  such  slight  changes  that  there 
is  no  line  showing  where  one  kind  leaves  off  and  another 


354 


BIOLOGY   AND    ITS    MAKERS 


begins.  Thus  their  history  for  thousands  of  years  bears 
testimony  to  the  fact  that  the  species  have  not  remained 
constant,  but  have  changed  into  other  species. 

Fig.  103  will  give  an  idea  of  the  varieties  and  gradations. 
It  represents  shells  of  a  genus,  Paludina,  which  is  still  abun- 
dant in  most  of  the  fresh  waters  of  our  globe. 


Fig.   103. — Transmutations  of  Paludina.     (After  Neumayer.) 


A  similar  series  of  shells  has  been  brought  to  light  in 
Wiirttemberg  in  which  the  variations  pass  through  wider 
limits,  so  that  not  only  different  species  may  be  observed, 
but  different  genera  connected  by  almost  insensible  grada- 
tions.    These  transformations  are  found  in  a  little  flattened 


ORGANIC    EVOLUTION 


355 


pond-shell    similar  to  the  planorbis,  which  is  so  common  at 
the  present  time. 

Fig.  104  shows  some  of  these  transformations,  the  finer 


I 


S^ 


20 


^^=^^ 


^ 


c:^::> 


22^ 


<:i23 


<m^ 


c^-^fii^ 


JV 


Fig.    104. — Planorbis  Shells  from  Steinheim.      (After  Hyatt.) 

gradations  being  omitted.  The  shells  from  these  two  sources 
bear  directly  upon  the  question  of  whether  or  not  species  have 
held  rigidly  to  their  original  form. 


356  BIOLOGY   AND    ITS    MAKERS 

After  this  kind  of  revelation  in  reference  to  lower  animals, 
we  turn  with  awakened  interest  to  the  fossil  bones  of  the 
higher  animals. 

Evolution  of  the  Horse. — When  we  take  into  account  the 
way  in  which  fossils  have  been  produced  we  see  clearly  that 
it  is  the  hard  parts,  such  as  the  shells  and  the  bones,  that  will 
be  preserved,  while  the  soft  parts  of  animals  will  disappear. 
Is  it  not  possible  that  we  may  find  the  fossil  bones  of  higher 
animals  arranged  in  chronological  order  and  in  sufficient 
number  to  supplement  the  testimony  of  the  shells?  There 
has  been  preserved  in  the  rocks  of  our  Western  States  a  very 
complete  history  of  the  evolution  of  the  horse  family,  written, 
as  it  were,  on  tablets  of  stone,  and  extending  over  a  period 
of  more  than  two  million  years,  as  the  geologists  estimate 
time.  Geologists  can,  of  course,  measure  the  thickness  of 
rocks  and  form  some  estimate  of  the  rate  at  which  they  were 
deposited  by  observing  the  character  of  the  material  and  com- 
paring the  formation  with  similar  water  deposits  of  the 
present  time.  Near  the  surface,  in  the  deposits  of  the 
quarternary  period,  are  found  remains  of  the  immediate 
ancestors  of  the  horse,  which  are  recognized  as  belonging 
to  the  same  genus,  Equus,  but  to  a  different  species;  thence, 
back  to  the  lowest  beds  of  the  tertiary  period  we  come 
upon  the  successive  ancestral  forms,  embracing  several  dis- 
tinct genera  and  exhibiting  an  interesting  series  of  trans- 
formations. 

If  in  this  way  we  go  into  the  past  a  half-million  years,  we 
find  the  ancestors  of  the  horse  reduced  in  size  and  with  three 
toes  each  on  the  fore  and  hind  feet.  The  living  horse  now 
has  only  a  single  toe  on  each  foot,  but  it  has  small  splint-like 
bones  that  represent  the  rudiments  of  two  more.  If  we  go 
back  a  million  years,  we  find  three  toes  and  the  rudiments 
of  a  fourth;  and  going  back  two  million  years,  we  find  four 
fully  developed  toes,  and  bones  in  the  feet  to  support  them. 


ORGANIC    EVOLUTION  357 

It  is  believed  that  in  still  older  rocks  a  five-toed  form  will  be 
discovered,  which  was  the  parent  of  the  four- toed  form. 

In  the  collections  at  Yale  College  there  are  preserved 
upward  of  thirty  steps  or  stages  in  the  history  of  the  horse 
family,  showing  that  it  arose  by  evolution  or  gradual  change 
from  a  four-  or  five- toed  ancestor  of  about  the  size  of  a  fox, 
and  that  it  passed  through  many  changes,  besides  increase 
in  size,  in  the  two  million  years  in  which  we  can  get  facts 
as  to  its  history. 

Remarkable  as  is  this  feature  of  the  Marsh  collection  at 
New  Haven,  it  is  now  surpassed  by  that  in  the  Museum  of 
Natural  History  in  New  York  City.  Here,  through  the 
munificent  gifts  of  the  late  W.  C.  Whitney,  there  has  been 
accumulated  the  most  complete  and  extensive  collection  of 
fossil  horses  in  the  world.  This  embraced,  in  1904,  some 
portions  of  710  fossil  horses,  146  having  been  derived  from 
explorations  under  the  Whitney  fund.  The  extraordinary 
character  of  the  collection  is  shown  from  the  fact  that  it 
contains  five  complete  skeletons  of  fossil  horses — more  than 
existed  at  that  time  in  all  other  museums  of  the  world. 

The  specimens  in  this  remarkable  collection  show  phases  in 
the  parallel  development  of  three  or  four  distinct  races  of  horse- 
like animals,  and  this  opens  a  fine  problem  in  comparative 
anatomy;  viz.,  to  separate  those  in  the  direct  line  of  ancestry 
of  our  modem  horse  from  all  the  others.  This  has  been 
accomplished  by  O shorn,  and  through  his  critical  analysis 
we  have  become  aware  of  the  fact  that  the  races  of  fossil 
horses  had  not  been  distinguished  in  any  earlier  studies. 
As  a  result  of  these  studies,  a  new  ancestry  of  the  horse, 
differing  in  details  from  that  given  by  Huxley  and  Marsh,  is 
forthcoming. 

Fig.  105  shows  the  bones  of  the  foreleg  of  the  modem 
horse,  and  Fig.  106  some  of  the  modifications  through  which 
it  has  passed.     Fig.  107  shows  a  reconstruction  of  the  ances- 


358 


BIOLOGY   AND    ITS    MAKERS 


tor  of  the  horse  made  by  Charles  R.  Knight,  the  animal 
painter,  under  the  direction  of  Professor  O shorn. 

While  the  limbs  were  undergoing  the  changes  indicated, 
other  parts  of  the  organism  were  also  being  transformed 


Fig.    105. — Bones  of  the  Foreleg  and  Hindleg  of  a  Horse. 

and  adapted  to  the  changing  conditions  of  its  life.  The 
evolution  of  the  grinding  teeth  of  the  horse  is  fully  exhibited 
in  the  fossil  remains.  All  the  facts  bear  testimony  that 
the  horse  was  not  originally  created  as  known  to-day,  but 
that  his  ancestors  existed  in  different  forms,  and  in  evolution 
have  transcended  several  genera  and  a  considerable  num- 
ber of  species.  The  highly  specialized  limb  of  the  horse 
adapted  for  speed  was  the  product  of  a  long  series  of  changes, 


ORGANIC    EVOLUTION 


359 


of  which  the  record  is  fairly  well  preserved.  Moreover,  the 
records  show  that  the  atavus  of  the  horse  began  in  North 
America,  and  that  by  migration  the  primitive  horses  spread 
from  this  continent  to  Europe,  Asia,  and  Africa. 

So  far  we  have  treated  the  question  of  fixity  of  species  as 
a  historical  one,  and  have  gone  searching  for  clues  of  past 


Fig.   io6. — Bones  of  the   Foreleg  and  Molar  Teeth  of   Fossil  Ancestors 
of  the  Horse.     European  Forms.     (After  Kayser.) 

conditions  just  as  an  archaeologist  explores  the  past  in  buried 
cities.  The  facts  we  have  encountered,  taken  in  connection 
with  a  multitude  of  others  pointing  in  the  same  direction, 
begin  to  answer  the  initial  question.  Were  the  immense  num- 
bers of  living  forms  created  just  as  we  find  them,  or  were 
they  evolved  by  a  process  of  transformation  ? 


36o  BIOLOGY   AND    ITS    MAKERS 

The  geological  record  of  other  families  of  mammals  has 
also  been  made  out,  but  none  so  completely  as  that  of  the 
horse  family.  The  records  show  that  the  camels  were  native 
in  North  America,  and  that  they  spread  by  migration  from 
the  land  of  their  birth  to  Asia  and  Africa,  probably  crossing 
by  means  of  land-connections  which  have  long  since  become 
submerged. 

The  geological  record,  considered  as  a  whole,  shows  that 
the  earlier  formed  animals  were  representatives  of  the  lower 
groups,  and  that  when  vertebrate  animals  were  formed,  for 
a  very  long  time  only  fishes  were  living,  then  amphibians,, 
reptiles,  birds,  and  finally,  after  immense  reaches  of  time,, 
mammals  began  to  appear. 

Connecting  Forms. — Interesting  connecting  forms  be- 
tween large  groups  sometimes  are  found,  or,  if  not  connecting 
forms,  generalized  ones  embracing  the  structural  character- 
istics of  two  separate  groups.  Such  a  form  is  the  archa^op- 
teryx  (Fig.  io8),  a  primitive  bird  with  reptilian  anatomy,, 
with  teeth  in  its  jaws,  and  a  long,  lizard-like  tail  covered  with 
feathers,  which  seems  to  show  connection  between  birds  and 
reptiles.  The  wing  also  shows  the  supernumerary  fingers,, 
which  have  been  suppressed  in  modem  birds.  Another  sug- 
gestive type  of  this  kind  is  the  flying  reptile  or  pterodactyl,. 
of  which  a  considerable  number  have  been  discovered. 
Illustrations  indicating  that  animals  have  had  a  common  line 
of  descent  might  be  greatly  multiphed. 

The  Embryological  Record  and  its  Connection  with  Evo- 
lution.— The  most  interesting,  as  well  as  the  most  compre- 
hensive clues  bearing  on  the  evolution  of  animal  life  are 
found  in  the  various  stages  through  which  animals  pass  on 
their  way  from  the  egg  to  the  fully  formed  animal.  All 
animals  above  the  protozoa  begin  their  lives  as  single  cells,, 
and  between  that  rudimentary  condition  and  the  adult  stage 
every  gradation  of  structure  is  exhibited.     As  animals  de- 


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362 


BIOLOGY   AND    ITS    MAKERS 


velop  they  become  successively  more  and   more  complex, 
and  in  their  shifting  history  many  rudimentary  organs  arise 


Fig.   108. — Fossil   Remains  of  a   Primitive   Bird  (Archeopteryx). 
From  the  specimen  in  the  Beriin  Museum.     (After  Kayser.) 


and  disappear.     For  illustration,  in  the  young  chick,  devel- 
oping within  the  hen's  egg,  there  appear,  after  three  or  four 


ORGANIC    EVOLUTION 


Z^3 


days  of  incubation,  gill-slits,  or  openings  into  the  throat, 
like  the  gill-openings  of  lower  fishes.  These  organs  belong 
primarily  to  water  life,  and  are  not  of  direct  use  to  the  chick. 


Fig.   109. — The  Gill-clefts  of  a  Shark  (upper  fig.)  Compared  with 
Those  of  the  Embryonic  Chick  (to  the  left)   and  Rabbit. 


The  heart  and  the  blood-vessels  at  this  stage  are  also  of  the 
fish-like  type,  but  this  condition  does  noi  last  long;  the  gill- 
slits,  or  gill-clefts,  fade  away  within  a  few  days,  and  the 


364 


BIOLOGY   AND    ITS    MAKERS 


arteries  of  the  head  and  the  neck  undergo  great  changes  long 
before  the  chick  is  hatched.  Similar  gill-clefts  and  similar 
arrangements  of  blood-vessels  appear  also  very  early  in  the 
development  of  the  young  rabbit,  and  in  the  development 
of  all  higher  life.  Except  for  the  theory  of  descent,  such 
things  would  remain  a  lasting  enigma.  The  universal  pres- 
ence of  gill-clefts  is  not  to  be  looked   on  as  a  haphazard 


Fig. 


-The  Jaws  of  an  Embryonic  Whale,  Showing  Rudimentary 
Teeth. 


occurrence.  They  must  have  some  meaning,  and  the  best 
suggestion  so  far  offered  is  that  they  are  survivals  inherited 
from  remote  ancestors.  The  higher  animals  have  sprung 
from  simpler  ones,  and  the  gill- slits,  along  with  other  rudi- 
mentary organs,  have  been  retained  in  their  history.  It  is 
not  necessary  to  assume  that  they  are  inherited  from  adult 
ancestors;  they  are,  more  likely,  embryonic  structures  still 
retained  in  the  developmental  history  of  higher  animals. 


ORGANIC    EVOLUTION  365 

Such  traces  are  like  inscriptions  on  ancient  columns — they 
are  clues  to  former  conditions,  and,  occurring  in  the  animal 
series,  they  weigh  heavily  on  the  side  of  evolution. 

An  idea  of  the  appearance  of  gill-clefts  may  be  obtained 
from  Fig.  109  showing  the  gill- clefts  in  a  shark  and  those  In 
the  embryo  of  a  chick  and  a  rabbit. 

Of  a  similar  nature  are  the  rudimentary  teeth  in  the  jaws 
of  the  embryo  of  the  whalebone  whale  (Fig.  no).  The 
adults  have  no  teeth,  these  appearing  only  as  transitory  rudi- 
ments in  the  embryo.  It  is  to  be  assumed  that  the  teeth  are 
inheritances,  and  that  the  toothless  baleen  whale  is  derived 
from  toothed  ancestors. 

If  we  now  turn  to  comparative  anatomy,  to  classification, 
and  to  the  geographical  distribution  of  animals,  we  find  that 
it  is  necessary  to  assume  the  doctrine  of  descent  in  order 
to  explain  the  observed  facts;  the  evidence  for  evolution, 
indeed,  becomes  cumulative.  But  it  is  not  necessary,  nor 
will  space  permit,  to  give  extended  illustrations  from  these 
various  departments  of  biological  researches. 

The  Human  Body. — Although  the  broad  doctrine  of  evo- 
lution rests  largely  upon  the  observation  of  animals  and  plants, 
there  is  naturally  unusual  interest  as  to  its  teaching  in  ref- 
erence to  the  development  of  the  human  body.  That  the 
human  body  belongs  to  the  animal  series  has  long  been 
admitted,  and  that  it  has  arisen  through  a  long  series  of 
changes  is  shown  from  a  study  of  its  structure  and  develop- 
ment. It  retains  marks  of  the  scaffolding  in  its  building. 
The  human  body  has  the  same  devious  course  of  embryonic 
development  as  that  of  other  mammals.  In  the  course  of 
its  formation  gill-clefts  make  their  appearance;  the  circula- 
tion is  successively  that  of  a  single-,  a  double-,  and  a  four- 
chambered  heart,  with  blood-vessels  for  the  gill-clefts.  Time 
and  energy  are  consumed  in  building  up  rudimentary  struc- 
tures which  are  evanescent  and  whose  presence  can  be  best 


366  BIOLOGY   AND    ITS   MAKERS 

explained  on  the  assumption  that  they  are,  as  in  other  animals, 
hereditary  survivals. 

Wiedersheim  has  pointed  out  more  than  one  hundred 
and  eighty  rudimentary  or  vestigial  structures  belonging  to 
the  human  body,  which  indicate  an  evolutionary  relation- 
ship with  lower  vertebrates.  It  would  require  a  considerable 
treatise  to  present  the  discoveries  in  reference  to  man's 
organization,  as  Wiedersheim  has  done  in  his  Structure  of 
Man.  As  passing  illustrations  of  the  nature  of  some  of  these 
suggestive  things  bearing  on  the  question  of  man's  origin 
may  be  mentioned :  the  strange  grasping  power  of  the  newly 
bom  human  infant,  retained  for  a  short  time,  and  enabling 
the  babe  to  sustain  its  weight;  the  presence  of  a  tail  and 
rudimentary  tail  muscles;  of  rudimientary  ear  muscles;  of 
gill-clefts,  etc. 

Antiquity  of  Man. — ^The  story  of  prehistoric  man  is  im- 
perfectly known,  although  sporadic  explorations  have  already 
accumulated  an  interesting  series  of  evidences  bearing  on 
the  subject,  such  as  primitive  stone  implements  of  human 
manufacture,  crude  sketches  of  extinct  animals  by  prehistoric 
artists,  and  fossil  remains  of  primitive  man  showing  grada- 
tions in  the  shape  and  capacity  of  skulls.  All  these  cor- 
related sources  afford  most  convincing  proofs  of  man's 
great  antiquity.  He  has  left  traces  of  his  occupancy  of 
the  Earth,  especially  in  central  and  southwestern  Europe 
and  in  England,  long  before  the  davm  of  the  historical 
period. 

The  prehistoric  stone  implements  are  found  associated 
with  the  bones  of  extinct  animals  in  caves,  and  imbedded  in 
the  strata  of  soil  and  gravel  that  have  remained  undisturbed 
for  many  centuries.  They  are  of  three  grades:  neoliths,  the 
more  recent  ones,  carefully  shaped  with  skill  and  artistic 
feeling;  palaeoliths,  very  ancient,  rude,  but  evidently  shaped 
by  design;  and  eoliths,  rough  stone  chips  bearing  evidence  of 


ORGANIC   EVOLUTION  367 

use  and  indicating  the  existence  of  man  of  less  developed 
skill.  These  latter  implements  carry  the  traces  of  a  tool- 
making  creature  back  into  the  Tertiary  period. 

Besides  the  stone  implements  there  are  many  sketches  of 
extinct  animals  by  prehistoric  artists,  scratched  on  bone, 
ivory,  slate,  and  on  the  walls  of  caves.  The  inference  to  be 
drawn  from  these  sketches  is  that  man  was  alive  in  central 
and  southwestern  Europe  when  the  hairy  mammoth  and 
the  reindeer  occupied  the  same  territory.  The  crude  sketches 
of  palaeolithic  man,  just  referred  to,  merge  by  gradations 
into  the  more  carefully  drawn,  and  sometimes  colored 
sketches,  of  neoHthic  man.  Those  of  the  Cave  of  Altamira, 
in  Spain,  are  very  notable  products  of  neoHthic  artists.  They 
have  been  described  and  many  of  them  reproduced  in  colored 
illustrations  in  Cartailhac  and  Breuil's  La  Caverne  d' Altamira, 
(1906) .    They  represent  the  golden  period  of  prehistoric  art. 

The  range  of  discovery  of  fossil  human  relics  gives  evidence 
of  a  wide  geographical  distribution  of  primitive  races  during 
the  palaeohthic  time.  Variations  in  the  degree  of  skill  in 
the  manufacture  of  stone  implements,  as  well  as  in  other 
particulars,  have  brought  to  archaeologists  the  recognition  of 
different  culture  periods,  which  are  well  exhibited  in  different 
parts  of  France  and  Central  Europe.  Not  less  than  six  cul- 
ture periods  of  palaeolithic  man  are  recognized,  indicating 
that  the  prehistoric  period  of  human  development  was  far 
longer  than  the  entire  historic  period. 

It  is,  however,  to  fossil  remains  of  primitive  man  that  we 
must  look  for  evidences  of  structural  changes  that  have 
taken  place  in  the  human  frame. 

Of  all  the  bony  parts  the  skull  is  the  most  interesting  for 
comparison,  since  its  size  and  configuration  indicate  in  a 
general  way  the  degree  of  development  of  the  brain,  and,  as 
a  consequence,  the  relative  grade  of  intelligence. 

One  of  the  most  famous  documents  of  ancestral  history  is 


368  BIOLOGY  AND   ITS  MAKERS 

the  well-known  Neanderthal  skull,  discovered  in  a  cave  near 
Diisseldorf  in  the  valley  of  the  Neander,  in  1856  and  first 
described  in  1857.  It  is  now  exhibited  with  other  parts  of 
the  skeleton  in  the  provincial  museum  at  Bonn  on  the  Rhine. 
The  inferences  drawn  from  the  anatomical  study  of  this 
very  ancient  skull,  with  its  low  receding  forehead,  showing 
small  development  in  the  region  of  the  higher  mental  facul- 
ties, created  a  sensation,  and  great  opposition  was  developed 
to  allowing  the  discovery  to  rank  as  an  evidence  of  primitive 
man.  But  its  importance  has  become  enhanced  by  the  dis- 
covery of  a  long  series  of  similar  skulls.  In  1886  came  the 
discovery  in  the  Cave  of  Spy,  Belgium,  of  two  skeletons  with 
the  same  structural  features  as  those  of  the  Neanderthal 
remains,  and  since  that  time  the  discoveries  of  numerous 
similar  relics  have  established  the  existence  of  a  Neanderthal 
race  Hving  in  the  middle  of  the  palaeolithic  period.  The  more 
notable  members  of  the  Neanderthaloid  series  embrace:  the 
human  remains  of  Krapina,  in  Croatia,  found  in  1899- 1904, 
and  consisting  of  parts  of  the  skeletons  of  ten  persons  from 
infancy  to  old  age;  the  skeletal  remains  of  La  Chapelle  aux- 
Saints  and  of  Le  Moustier.  In  August,  1908,  there  was  dis- 
covered in  Southwestern  France  (Correze),  by  well  directed 
efforts  of  French  archaeologists,  a  very  interesting  skeleton 
of  the  Neanderthal  type,  and  now  known  as  the  man  of  La 
Chapelle  aux-Saints.  This  is  the  skeleton  of  an  old  man  with 
an  almost  complete  skull,  and  a  lower  jaw  lacking  some  of  the 
teeth.  Since  the  comprehensive  analysis  of  these  remains, 
published  by  Boule  in  19 13,  this  is  the  most  thoroughly 
known  skeleton  of  the  Neanderthal  race  and  may  be  taken 
as  a  type.  Besides  the  structural  features  of  the  bony  parts, 
it  is  interesting  to  note  that  the  casts  of  the  interior  of  the 
cranium  show  the  surface  features  of  the  brain.  As  com- 
pared with  the  brain  of  modern  man,  it  is  small  in  the  region 
of  the  frontal  lobes  and  shows  a  greater  simplicity  in  the 


ORGANIC  EVOLUTION  369 

pattern  of  the  convolutions.  A  somewhat  more  primitive 
type  was  discovered  a  few  months  earlier  (March,  1908)  at 
the  famous  station  of  Le  Moustier  (Dordogne).  It  is  the 
skull  of  a  young  person  and  valuable  for  comparison.  These 
human  relics  of  the  Neanderthal  age  have  been  named  scien- 
tifically Homo  neanderthalensis  (or  primigenius) ,  Homo  mou- 
stierensis,  etc.,  thus  including  them  in  the  same  genus  with 
Homo  sapiens  of  Linnaeus. 

These  aboriginal  people  represent  one  link  of  the  chain  of 
human  ancestry,  and  they  were  followed  by  a  more  developed 
type  of  primitive  man  before  the  dawn  of  history,  and  the 
emergence  of  the  modern  type. 

A  much  more  interesting  circumstance  is  that  the  Neander- 
thal people  were  also  preceded  by  more  primitive  pre-humans. 
There  are  known  at  present  three  examples  of  remains  that 
are  distinctly  pre-Neanderthaloid.  The  first  to  be  discov- 
ered, and  also  the  most  primitive  pre-human  species  known, 
is  represented  by  portions  of  the  skull  and  of  the  leg  bones, 
found  in  Central  Java  by  the  Dutch  surgeon,  Dubois,  during 
the  years  1891  and  1892,  and  made  known  in  1894.  These 
remains  were  found  in  tertiary  deposits  and  were  baptized 
under  the  name  of  Pithecanthropus  erectus.  The  capacity  of 
the  skull,  930  cubic  centimeters,  precludes  the  conclusion 
that  it  belongs  to  the  anthropoid  series;  the  largest  cranial 
capacity  of  apes,  living  or  fossil,  not  exceeding  600  cubic 
centimetres. 

The  second  pre-Neanderthaloid  is  the  perfect  lower  jaw 
with  all  the  teeth,  discovered  in  1907  in  the  sands  of  Mauer, 
near  Heidelberg.  These  deposits  belong  to  the  lower  quarter- 
nary,  and  since  the  discovery  of  the  Heidelberg  jaw  it  is 
claimed  that  Eoliths  have  been  discovered  in  the  same  layer. 
The  jaw,  while  distinctly  human  as  to  characteristics  of  the 
teeth,  is  very  primitive.  The  creature  to  which  it  belonged 
has  been  designated  Homo  Heidelbergensis. 


370  BIOLOGY  AND  ITS  MAKERS 

The  most  recent  discovery  of  pre-human  remains  comes 
from  England.  At  Piltdown  Common,  in  Sussex,  in  191 2, 
there  was  unearthed  a  skull,  with  parts  of  the  lower  jaw  and 
teeth,  that  fits  into  the  series  of  the  pre-Neanderthaloid. 
It  has  been  suggestively  named  the  dawn  man  {Eoanthropus 
Dawsonii).  The  controversies  of  Dr.  Smith-Woodward  and 
Professor  Keith  over  details  of  the  reconstruction  of  missing 
parts,  and  the  estimated  capacity  of  the  skull,  were  given 
wide  publicity  through  the  periodical  Nature.  They  are 
technical  and  do  not  materially  affect  the  question  of  the 
great  antiquity  of  this  skull  and  its  relative  position  in  the 
series. 

Above  the  Neanderthal  race  come  the  numerous  fossil 
remains  of  Neolithic  man,  merging  by  structural  gradations 
into  those  of  recent  type.  The  skeleton  of  Men  tonne,  that 
of  Combe  Chapelle  (1909),  of  Galley  Hill  (1895),  the  skull  of 
Engis,  the  cro-mangon  race,  and  other  representatives,  are 
the  forms  that  connect  palaeoHthic  with  recent  man. 

Putting  these  discoveries  together  we  have  an  interesting 
series  of  gradations  of  skulls,  leading  one  into  the  other,  and 
covering  a  range  of  cranial  capacity  from  930  cu.  cm.,  that 
of  the  Java  man,  to  1480-1555  cu.  cm.,  that  of  the  average 
adult  white  European.  The  Neanderthal  skulls  occupy  an 
intermediate  position  with  a  cranial  capacity  of  approxi- 
mately 1400  cu.  cm. 

Figure  in  shows  in  outline  profile  reconstructions  of  some 
of  the  fossil  types  as  compared  with  the  short-headed  type  of 
Europe. 

In  tracing  backwards  from  recent  man,  it  is  not  to  be  as- 
sumed that  the  ancestral  line  breaks  off  abruptly.  Even  the 
Java  man  had  antecedents,  and  it  is  natural  to  assume  his 
derivation  from  an  extinct  primate  of  the  earlier  tertiary  de- 
posits. Positive  evidences  are  lacking,  but  the  known  pres- 
ence of  anthropomorphous  primates  in  the  Miocene  of  France 


ORGANIC  EVOLUTION  j^yi 

offers  a  possible  suggestion.  Osborn  (19 lo)  has  pointed  out 
that  ''The  only  known  Miocene  and  Pliocene  primate  which 
might  be  considered  an  'Eolith'  maker  is  Dryopithecus;  all 
others  belong  to  existing  phyla  of  monkeys,  baboons,  and 
apes."  Palaeontological  discoveries  have  supplied  the  line 
of  genealogy  of  several  families  of  mammals,  and  if,  on  this 
basis,  we  assume  that  man  and  the  anthropoid  apes  had  a 
generalized  ancestor,  it  is  nevertheless  clear  that  the  human 
and  the  simian  Knes  have  had  an  independent  development 
for  many  centuries.  There  has  been  no  crossing  of  the  lines 
since  tertiary  times. 


Fig.  I II. — Profile  Reconstructions  of  the  Skulls  of  Living  and 
Fossil  Men:  i.  Brachycephalic  European;  2.  The  more  ancient 
of  the  Nebraska  skulls;  3.  The  Neanderthal  man;  4.  One  of  the 
Spy  skulls;  5.  Skull  of  the  Java  man.  (Altered  from  Schwalbe 
and  Osborn.) 

The  derivation  of  man  from  an  extinct  tertiary  Primate 
seems  already  to  be  well  authenticated.  Furthermore,  the 
fossil  records  give  evidence  of  the  conditions  under  which  the 
development  of  the  higher  races  of  animals  began.  By  mak- 
ing casts  of  the  interior  of  the  fossil  skulls  of  tertiary  mam- 


372  BIOLOGY  AND  ITS  MAKERS 

mals,  it  has  been  determined  that  there  was  in  that  geological 
period  a  marked  increase  in  the  size  of  the  brain.  This  cir- 
cumstance was  of  the  greatest  importance  both  for  progress 
and  for  perpetuity  of  certain  kinds  of  animals.  Those  in 
particular  whose  increased  intelligence  enabled  them  to  cope 
more  successfully  with  the  conditions  of  their  existence,  and 
to  turn  natural  forces  to  their  advantage,  were  continued  and 
improved.  In  pre-humans  the  increase  in  brain  surface  led 
to  the  power  of  storing  up  mental  impressions  and  experi- 
ences, and,  finally,  brought  about  a  condition  of  educability 
which  formed  the  starting  point  for  marked  improvement. 

Mental  Evolution. — Already  the  horizon  is  being  wid- 
ened, and  new  problems  in  human  evolution  have  been  opened. 
The  evidences  in  reference  to  the  evolution  of  the  human 
body  are  so  compelling  as  to  be  already  generally  accepted, 
and  we  have  now  the  question  of  evolution  of  mentality  to 
deal  with.  The  progressive  intelligence  of  animals  is  shown 
to  depend  upon  the  structure  of  the  brain  and  the  nervous 
syste"ta,  and  there  exists  such  a  finely  graded  series  in  this 
respect  that  there  is  strong  evidence  of  the  derivation  of  hu- 
man faculties  from  brute  faculties. 

Sweep  of  the  Doctrine  of  Evolution. — The  great  sweep 
of  the  doctrine  of  evolution  makes  it  ''one  of  the  greatest 
acquisitions  of  human  knowledge."  There  has  been  no 
point  of  intellectual  vantage  reached  which  is  more  inspiring. 
It  is  so  comprehensive  that  it  enters  into  all  realms  of  thought. 
Weismann  expresses  the  opinion  that  ''the  theory  of  descent 
is  the  most  progressive  step  that  has  been  taken  in  the  devel- 
opment of  human  knowledge,"  and  says  that  this  position 
"is  justified,  it  seems  to  me,  even  by  this  fact  alone:  that  the 
evolution  idea  is  not  merely  a  new  light  on  the  special  region 
of  biological  sciences,  zoology  and  botany,  but  is  of  quite 
general  importance.  The  conception  of  an  evolution  of  life 
upon  the  earth  reaches  far  beyond  the  bounds  of  any  sin- 


ORGANIC  EVOLUTION  373 

gle  science,  and  influences  our  whole  realm  of  thought.  It 
means  nothing  less  than  the  elimination  of  the  miraculous 
from  our  knowledge  of  nature,  and  the  placing  of  the  phe- 
nomena of  life  on  the  same  plane  as  the  other  natural  proc- 
esses, that  is,  as  having  been  brought  about  by  the  same 
forces  and  being  subject  to  the  same  laws." 

One  feature  of  the  doctrine  is  very  interesting;  it  has 
enabled  anatomists  to  predict  that  traces  of  certain  structures 
not  present  in  the  adult  will  be  found  in  the  embryonic  condi- 
tion of  higher  animals,  and  by  the  verification  of  these  predic- 
tions, it  receives  a  high  degree  of  plausibility.  The  presence 
of  an  OS  centrale  in  the  human  wrist  was  predicted,  and  after- 
ward found,  as  also  the  presence  of  a  rudimentary  thirteenth 
rib  in  early  stages  of  the  human  body.  The  predictions,  of 
course,  are  chiefly  technical,  but  they  are  based  on  the  idea 
of  common  descent  and  adaptation. 

It  took  a  long  time  even  for  scientific  men  to  arrive  at  a 
belief  in  the  continuity  of  nature,  and  having  arrived  there, 
it  is  not  easy  to  surrender  it.  There  is  no  reason  to  think 
that  the  continuity  is  broken  in  the  case  of  man's  develop- 
ment. Naturalists  have  now  come  to  accept  as  a  mere  state- 
ment of  a  fact  of  nature  that  the  vast  variety  of  forms  of  life 
upon  our  globe  has  been  produced  by  a  process  of  evolution. 
If  this  position  be  admitted,  the  next  question  would  be, 
What  are  the  factors  which  have  been  operative  to  bring  this 
about?  This  brings  us  naturally  to  discuss  the  theories  of 
evolution. 


CHAPTER  XVII 

THEORIES  OF  EVOLUTION:   LAMARCK,  DARWIN 

The  impression  so  generally  entertained  that  the  doctrine 
of  organic  evolution  is  a  vague  hypothesis,  requiring  for  its 
support  great  stretches  of  the  imagination,  gives  way  upon  an 
examination  of  the  facts,  and  we  come  to  recognize  that  it  is 
a  well-founded  theory,  resting  upon  great  accumulations  of 
evidence.  If  the  matter  could  rest  here,  it  would  be  rela- 
tively simple;  but  it  is  necessary  to  examine  into  the  causes 
of  the  evolutionary  process.  While  scientific  observation  has 
shown  that  species  are  not  fixed,  but  undergo  transforma- 
tions of  considerable  extent,  there  still  remains  to  be  accounted 
for  the  way  in  which  these  changes  have  been  produced. 

One  may  assume  that  the  changes  in  animal  life  are  the 
result  of  the  interaction  of  protoplasm  and  certain  natural 
agencies  in  its  surroundings,  but  it  is  evidently  a  very  diffi- 
cult matter  to  designate  the  particular  agencies  or  factors  of 
evolution  that  have  operated  to  bring  about  changes  in  spe- 
cies. The  attempts  to  indicate  these  factors  give  rise  to  differ- 
ent theories  of  evolution,  and  it  is  just  here  that  the  contro- 
versies concerning  the  subject  come  in.  We  must  remember, 
however,  that  to-day  the  controversies  about  evolution  are 
not  as  to  whether  it  was  or  was  not  the  method  of  creation, 
but  as  to  the  factors  by  which  the  evolution  of  different 
forms  was  accomplished.  Says  Packard:  "We  are  all  evo- 
lutionists, though  we  may  differ  as  to  the  nature  of  the 
efficient  causes." 

Of  the  various  theories  which  had  been  advanced  to 

374 


THEORIES    OF    LAMARCK    AND    DARWIN  375 

account  for  evolution,  up  to  the  announcement  of  the  muta- 
tion-theory of  De  Vries  in  1900,  three  in  particular  had 
commanded  the  greatest  amount  of  attention  and  been  the 
field  for  varied  and  extensive  discussion.  These  are  the 
theories  of  Lamarck,  Darwin,  and  Weismann.  They  are 
comprehensive  theories,  dealing  with  the  process  as  a  whole. 
Most  of  the  others  are  concerned  with  details,  and  emphasize 
certain  phases  of  the  process. 

Doubtless  the  factors  that  have  played  a  part  in  molding 
the  forms  that  have  appeared  in  the  procession  of  life  upon 
our  globe  have  been  numerous,  and,  in  addition  to  those  that 
have  been  indicated,  Osbom  very  aptly  suggests  that  there 
may  be  undiscovered  factors  of  evolution.  Within  a  few 
years  De  Vries  has  brought  into  prominence  the  idea  of  sudden 
transformations  leading  to  new  species,  and  has  accounted 
for  organic  evolution  on  that  basis.  Further  consideration  of 
this  theory,  however,  will  be  postponed,  while  in  the  present 
chapter  we  shall  endeavor  to  bring  out  the  salient  features 
of  the  theories  of  Lamarck  and  Darwin,  without  going  into 
much  detail  regarding  them. 

Lamarck 

Lamarck  was  the  first  to  give  a  theory  of  evolution  that 
has  retained  a  place  in  the  intellectual  world  up  to  the  present 
time,  and  he  may  justly  be  regarded  as  the  founder  of  that 
doctrine  in  the  modern  sense.  The  earlier  theories  w^ere 
more  restricted  in  their  reach  than  that  of  Lamarck.  Eras- 
mus Darwin,  his  greatest  predecessor  in  this  field  of  thought, 
announced  a  comprehensive  theory,  which,  while  suggestive 
and  forceful  in  originality,  was  diffuse,  and  is  now  only  of 
historical  interest.  The  more  prominent  writers  on  evo- 
lution in  the  period  prior  to  Lamarck  will  be  dealt  with  in 
the  chapter  on  the  Rise  of  Evolutionary  Thought. 


376  BIOLOGY   AND   ITS   MAKERS 

Lamarck  was  bom  in  1744,  and  led  a  quiet,  monotonous 
life,  almost  pathetic  on  account  of  his  struggles  with  poverty, 
and  the  lack  of  encouragement  and  proper  recognition  by  his 
contemporaries.  His  life  was  rendered  more  bearable,  how- 
ever, even  after  he  was  overtaken  by  complete  blindness, 
by  the  intellectual  atmosphere  that  he  created  for  himself, 
and  by  the  superb  confidence  and  affection  of  his  devoted 
daughter  Comelie,  who  sustained  him  and  made  the  truthful 
prediction  that  he  would  be  recognized  by  posterity  ("  La 
posterite  vous  honor era^^). 

His  Family. — He  came  of  a  military  family  possessing 
some  claims  to  distinction.  The  older  name  of  the  family 
had  been  de  Monet,  but  in  the  branch  to  which  Lamarck 
belonged  the  name  had  been  changed  to  de  Lamarque,  and 
in  the  days  of  the  first  Republic  was  signed  plain  I^amarck 
by  the  subject  of  this  sketch.  Jean  Baptiste  Lamarck  was 
the  eleventh  and  last  child  of  his  parents.  The  other  male 
members  of  the  family  having  been  provided  with  military 
occupations,  Jean  was  selected  by  his  father,  although 
against  the  lad's  own  wish,  for  the  clerical  profession,  and  ac- 
cordingly was  placed  in  the  college  of  the  Jesuits  at  Amiens. 
He  did  not,  however,  develop  a  taste  for  theological  studies, 
and  after  the  death  of  his  father  in  1760  "nothing  could 
induce  the  incipient  abbe,  then  seventeen  years  of  age, 
longer  to  wear  his  bands." 

His  ancestry  asserted  itself,  and  he  forsook  the  college  to 
follow  the  French  army  that  was  then  campaigning  in  Ger- 
many. Mounted  on  a  broken-down  horse  which  he  had  suc- 
ceeded in  buying  with  his  scanty  means,  he  arrived  on  the 
scene  of  action,  a  veritable  raw  recruit,  appearing  before 
Colonel  Lastic,  to  whom  he  had  brought  a  letter  of  recom- 
mendation. 

Military  Experience. — The  Colonel  would  have  liked  to 
be  rid  of  him,  but  owing  to  Lamarck's  persistence,  assigned 


THEORIES    OF    LAMARCK   AND    DARWIN  377 

him  to  a  company;  and,  being  mounted,  Lamarck  took  rank 
as  a  sergeant.  During  his  first  engagement  his  company 
was  exposed  to  the  direct  fire  of  the  enemy,  and  the  officers 
one  after  another  were  shot  until  Lamarck  by  order  of  suc- 
cession was  in  command  of  the  fourteen  remaining  gren- 
adiers. Akhough  the  French  army  retreated,  Lamarck 
refused  to  move  with  his  squad  until  he  received  directions 
from  headquarters  to  retire.  In  this  his  first  battle  he 
showed  the  courage  and  the  independence  that  characterized 
him  in  later  years. 

Adopts  Natural  Science. — An  injury  to  the  glands  of  the 
neck,  resulting  from  being  lifted  by  the  head  in  sport  by  one 
of  his  comrades,  unfitted  him  for  military  life,  and  he  went  to 
Paris  and  began  the  study  of  medicine,  supporting  himself 
in  the  mean  time  by  working  as  a  bank  clerk.  It  was  in  his 
medical  course  of  four  years'  severe  study  that  Lamarck 
received  the  exact  training  that  was  needed  to  convert  his 
enthusiastic  love  for  science  into  the  working  powers  of  an 
investigator.  He  became  especially  interested  in  botany, 
and,  after  a  chance  interview  with  Rousseau,  he  determined 
to  follow  the  ruling  passion  of  his  nature  and  devote  himself 
to  natural  science.  After  about  nine  years'  work  he  published, 
in  1778,  his  Flora  of  France,  and  in  due  course  was  appointed 
to  a  post  in  botany  in  the  Academy  of  Sciences.  He  did  not 
hold  this  position  long,  but  left  it  to  travel  with  the  sons 
of  Buffon  as  their  instructor.  This  agreeable  occupation 
extended  over  two  years,  and  he  then  returned  to  Paris,  and 
soon  after  was  made  keeper  of  the  herbarium  in  the  Royal 
Garden,  a  subordinate  position  entirely  beneath  his  merits. 
Lamarck  held  this  poorly  paid  position  for  several  years,  and 
was  finally  relieved  by  being  appointed  a  professor  in  the 
newly  established  Jardin  des  Plantes. 

He  took  an  active  part  in  the  reorganization  of  the  Royal 
Garden  (Jardin  du  Roi)  into  the  Jardin  des  Plantes.     When, 


378  BIOLOGY   AND    ITS    MAKERS 

during  the  French  Revolution,  everything  that  was  suggestive 
of  royalty  became  obnoxious  to  the  people,  it  was  Lamarck 
who  suggested  in  1790  that  the  name  of  the  King's  Garden 
be  changed  to  that  of  the  Botanical  Garden  (Jardin  des 
Plantes).  The  Royal  Garden  and  the  Cabinet  of  Natural 
History  were  combined,  and  in  1793  the  name  Jardin  des 
Plantes  proposed  by  Lamarck  was  adopted  for  the  in- 
stitution. 

It  was  through  the  endorsements  of  Lamarck  and  Geoffroy 
Saint-Hilaire  that  Cuvier  was  brought  into  this  great  scientific 
institution;  Cuvier,  who  was  later  to  be  advanced  above  him 
in  the  Jardin  and  in  public  favor,  and  who  was  to  break 
friendship  with  Lamarck  and  become  the  opponent  of  his 
views,  and  who  also  was  to  engage  in  a  memorable  debate 
with  his  other  supporter,  Saint-Hilaire. 

The  portrait  of  Lamarck  shown  in  Fig.  112  is  one  not 
generally  known.  Its  date  is  undetermined,  but  since  it  was 
published  in  Thornton's  British  Plants  in  1805,  we  know 
that  it  was  painted  before  the  publication  of  Lamarck's 
Philosophie  Zoologique,  and  before  the  full  force  of  the  cold- 
ness and  heartless  neglect  of  the  world  had  been  experienced. 
In  his  features  we  read  supremacy  of  the  intellect,  and  the 
unflinching  moral  courage  for  which  he  was  notable.  La- 
marck has  a  more  hopeful  expression  in  this  portrait  than  in 
those  of  his  later  years. 

Lamarck  Changes  from  Botany  to  Zoology. — Until  1794, 
when  he  was  fifty  years  of  age,  Lamarck  was  devoted  to 
botany,  but  on  being  urged,  after  the  reorganization  of  the 
Jardin  du  Roi,  to  take  charge  of  the  department  of  inverte- 
brates, he  finally  consented  and  changed  from  the  study  of 
plants  to  that  of  animals.  This  change  had  profound  in- 
fluence in  shaping  his  ideas.  He  found  the  invertebrates  in 
great  confusion,  and  set  about  to  bring  order  out  of  chaos, 
an  undertaking  in  which,  to  his  credit  be  it  acknowledged, 


THEORIES    OF    LAMARCK    AND    DARWIN  379 

he  succeeded.     The  fruit  of  his  labors,  the  Natural  His- 
tory of  Invertebrated  Animals   {Historie   naturelle  des  Ani- 


FiG.   112. — Lamarck,     1744-1829. 
From  Thornton's  British  Plants,  1805. 

maux  sans  Vertebres,  181 5-1822),  became  a  work  of  great 
importance.  He  took  hold  of  this  work,  it  should  be  re- 
membered, as  an  expert  observer,  trained  to  rigid  analysis 


38o  BIOLOGY   AND    ITS    MAKERS 

by  his  previous  critical  studies  in  botany.  In  the  progress 
of  the  work  he  was  impressed  with  the  differences  in  ani- 
mals and  the  difficulty  of  separating  one  species  from  an- 
other. He  had  occasion  to  observe  the  variations  produced 
in  animals  through  the  influence  of  climate,  temperature, 
moisture,  elevation  above  the  sea-level,  etc. 

He  observed  also  the  effects  of  use  and  disuse  upon  the 
development  of  organs:  the  exercise  of  an  organ  leading  to 
its  greater  development,  and  the  disuse  to  its  degeneration. 
Numerous  illustrations  are  cited  by  Lamarck  which  serve  to 
make  his  meaning  clear.  The  long  legs  of  wading  birds 
are  produced  and  extended  by  stretching  to  keep  above  the 
water;  the  long  neck  and  bill  of  storks  are  produced  by  their 
habit  of  life;  the  long  neck  of  the  giraffe  is  due  to  reaching 
for  fohage  on  trees;  the  web-footed  birds,  by  spreading 
the  toes  when  they  strike  the  water,  have  stimulated  the 
development  of  a  membrane  between  the  toes,  etc.  In  the 
reverse  direction,  the  loss  of  the  power  of  flight  in  the  ''wing- 
less" bird  of  New  Zealand  is  due  to  disuse  of  the  wings; 
while  the  loss  of  sight  in  the  mole  and  in  blind  cave  animals 
has  arisen  from  lack  of  use  of  eyes. 

The  changes  produced  in  animal  organization  in  this 
way  were  believed  to  be  continued  by  direct  inheritance  and 
improved  in  succeeding  generations. 

He  believed  also  in  a  perfecting  principle,  tending  to 
improve  animals — a  sort  of  conscious  endeavor  on  the  part 
of  the  animal  playing  a  part  in  its  better  development.  Fi- 
nally, he  came  to  believe  that  the  agencies  indicated  above 
were  the  factors  of  the  evolution  of  life. 

His  Theory  of  Evolution. — All  that  Lamarck  had  written 
before  he  changed  from  botany  to  zoology  (1794)  indicates 
his  belief  in  the  fixity  of  species,  which  was  the  prevailing 
notion  among  naturalists  of  the  period.  Then,  in  1800,  we 
find  him  apparently  all  at  once  expressing  a  contrary  opinion, 


THEORIES    OF   LAMARCK   AND    DARWIN  381 

and  an  opinion  to  which  he  held  unwaveringly  to  the  close 
of  his  life.  It  would  be  of  great  interest  to  determine  when 
Lamarck  changed  his  views,  and  upon  what  this  radical  rever- 
sal of  opinion  was  based;  but  we  have  no  sure  record  to 
depend  upon.  Since  his  theory  is  developed  chiefly  upon 
considerations  of  animal  life,  it  is  reasonable  to  assume  that 
his  evolutionary  ideas  took  form  in  his  mind  after  he  began 
the  serious  study  of  animals.  Doubtless,  his  mind  having 
been  prepared  and  his  insight  sharpened  by  his  earlier  studies, 
his  observations  in  a  new  field  supplied  the  data  which  led 
him  directly  to  the  conviction  that  species  are  unstable. 
As  Packard,  one  of  his  recent  biographers,  points  out,  the 
first  expression  of  his  new  views  of  which  we  have  any  record 
occurred  in  the  spring  of  1800,  on  the  occasion  of  his  opening 
lecture  to  his  course  on  the  invertebrates.  This  avowal  of 
belief  in  the  extensive  alteration  of  species  was  published  in 
1801  as  the  preface  to  his  Systeme  des  Animaux  sans 
Vertehres.  Here  also  he  foreshadowed  his  theory  of  evo- 
lution, saying  that  nature,  having  formed  the  simplest 
organisms,  ''then  with  the  aid  of  much  time  and  favor- 
able circumstances  .  .  .  formed  all  the  others."  It  has 
been  generally  believed  that  Lamarck's  first  public  ex- 
pression of  his  views  on  evolution  was  published  in  1802 
in  his  Recherches  sur  V Organisation  des  Corps  Vivans, 
but  the  researches  of  Packard  and  others  have  established 
the  earlier  date. 

Lamarck  continued  for  several  years  to  modify  and  am- 
plify the  expression  of  his  views.  It  is  not  necessary,  how- 
ever, to  follow  the  molding  of  his  ideas  on  evolution  as 
expressed  in  the  opening  lectures  to  his  course  in  the  years 
1 80c,  1802,  1803,  and  1806,  since  we  find  them  fully  elab- 
orated in  his  Philosophie  Zoologique,  published  in  1809, 
and  this  may  be  accepted  as  the  standard  source  for  the 
study  of  his  theory.     In  this  work  he  states  two  propositions 


382  BIOLOGY    AND    ITS    MAKERS 

under  the  name  of  laws,  which  have  been  translated  by 
Packard  as  follows! 

"  First  Law  :  In  every  animal  which  has  not  exceeded  the 
term  of  its  development,  the  more  frequent  and  sustained 
use  of  any  organ  gradually  strengthens  this  organ,  develops 
and  enlarges  it,  and  gives  it  a  strength  proportioned  to  the 
length  of  time  of  such  use;  while  the  constant  lack  of  use  of 
such  an  organ  imperceptibly  weakens  it,  causing  it  to  become 
reduced,  progressively  diminishes  its  faculties,  and  ends  in 
its  disappearance. 

"  Second  Law  :  Everything  which  nature  has  caused 
individuals  to  acquire  or  lose  by  the  influence  of  the  circum- 
stances to  which  their  race  may  be  for  a  long  time  exposed, 
and  consequently  by  the  influence  of  the  predominant  use  of 
such  an  organ,  or  by  that  of  the  constant  lack  of  use  of  such 
part,  it  preserves  by  heredity  and  passes  on  to  the  new  indi- 
viduals which  descend  from  it,  provided  that  the  changes 
thus  acquired  are  common  to  both  sexes,  or  to  those  which 
have  given  origin  to  these  new  individuals. 

''  These  are  the  two  fundamental  truths  which  can  be  mis- 
understood only  by  those  who  have  never  observed  or 
followed  nature  in  its  operations,"  etc.  The  first  law 
embodies  the  principle  of  use  and  disuse,  the  second  law  that 
of  heredity. 

In  1815  his  theory  received  some  extensions  of  minor 
importance.  The  only  points  to  which  attention  need  be 
called  are  that  he  gives  four  laws  instead  of  two,  and  that  a 
new  feature  occurs  in  the  second  law  in  the  statement  that 
the  production  of  a  new  organ  is  the  result  of  a  new  need 
(besoin)  which  continues  to  make  itself  felt. 

Simplified  Statement  of  Lamarck*s  Views. — For  practical 
exposition  the  theory  maybe  simplified  into  two  sets  of  facts: 
First,  those  to  be  classed  under  variation;  and,  second,  those 
under  heredity.     Variations  of  organs,  according  to  Lamarck,, 


THEORIES  OF  LAMARCK  AND  DARWIN    ^8^ 

arise  in  animals  mainly  through  use  and  disuse,  and  new 
organs  have  their  origin  in  a  physiological  need.  A  new  need 
felt  by  the  animal  impresses  itself  on  the  organism,  stimulating 
growth  and  adaptations  in  a  particular  direction.  This  part 
of  Lamarck's  theory  has  been  subjected  to  much  ridicule. 
The  sense  in  which  he  employs  the  word  besoin  has  been 
much  misunderstood;  when,  however,  we  take  into  ac- 
count that  he  uses  it,  not  merely  as  expressing  a  wish  or 
desire  on  the  part  of  the  animal,  but  as  the  reflex  action 
arising  from  new  conditions,  his  statement  loses  its  alleged 
grotesqueness  and  seems  to  be  founded  on  sound  physiology. 

Inheritance. — Lamarck's  view  of  heredity  was  uncritical;, 
according  to  his  conception,  inheritance  was  a  simple,  direct 
transmission  of  those  superficial  changes  that  arise  in  organs 
within  the  lifetime  of  an  individual  owing  to  use  and  disuse. 
It  is  on  this  question  of  the  direct  inheritance  of  variations 
acquired  in  the  lifetime  of  an  individual  that  his  theory  has 
been  the  most  assailed.  The  behef  in  the  inheritance  of 
acquired  characteristics  has  been  so  undermined  by  experi- 
mental evidence  that  at  the  present  time  we  can  not  point 
to 'a  single  unchallenged  instance  of  such  inheritance.  But, 
while  Lamarck's  theory  has  shown  weakness  on  that  side,, 
his  ideas  regarding  the  production  of  variations  have  been 
revived  and  extended. 

Variation. — The  more  commendable  part  of  his  theory 
is  the  attempt  to  account  for  variation.  Darwin  assumed 
variation,  but  Lamarck  attempted  to  account  for  it,  and  in 
this  feature  many  discerning  students  maintain  that  the 
theory  of  Lamarck  is  more  philosophical  in  its  foundation 
than  that  of  Darwin. 

In  any  theory  of  evolution  we  must  deal  with  the  variation 
of  organisms  and  heredity,  and  thus  we  observe  that  the  two 
factors  discussed  by  Lamarck  are  basal.  Although  it  must 
be  admitted  that  even  to-day  we  know  little  about  either 


384  BIOLOGY   AND   ITS   MAKERS 

variation  or  heredity,  they  remain  basal  factors  in  any  theory 
of  evolution. 

Time  and  Favorable  Conditions. — Lamarck  supposed  a 
very  long  time  was  necessary  to  bring  about  the  changes  which 
have  taken  place  in  animals.  The  central  thought  of  time 
and  favorable  conditions  occurs  again  and  again  in  his 
writings.  The  following  quotation  is  interesting  as  coming 
from  the  first  announcement  of  his  views  in  1800: 

*'  It  appears,  as  I  have  already  said,  that  time  and  favorable 
conditions  are  the  two  principal  means  which  nature  has 
employed  in  giving  existence  to  all  her  productions.  We 
know  that  for  her  time  has  no  limit,  and  that  consequently 
she  has  it  always  at  her  disposal. 

"As  to  the  circumstances  of  which  she  has  had  need  and 
of  which  she  makes  use  every  day  in  order  to  cause  her  pro- 
ductions to  vary,  we  can  say  that  in  a  manner  they  are 
inexhaustible. 

"The  essential  ones  arising  from  the  influence  and  from 
all  the  environing  media,  from  the  diversity  of  local  causes, 
of  habits,  of  movements,  of  action,  finally  of  means  of  living, 
of  preserving  their  lives,  of  defending  themselves,  of  mul- 
tiplying themselves,  etc.  Moreover,  as  the  result  of  these 
different  influences,  the  faculties,  developed  and  strengthened 
by  use,  become  diversified  by  the  new  habits  maintained  for 
long  ages,  and  by  slow  degrees  the  structure,  the  consistence — 
in  a  word,  the  nature,  the  condition  of  the  parts  and  of  the 
organs  consequently  participating  in  all  these  influences, 
became  preserved  and  were  propagated  by  heredity  (genera- 
tion)."    (Packard's  translation.) 

Salient  Points. — The  salient  points  in  Lamarck's  theory 
may  be  compacted  into  a  single  sentence:  It  is  a  theory  of 
the  evolution  of  animal  life,  depending  upon  variations 
brought  about  mainly  through  use  and  disuse  of  parts, 
and  also  by  responses  to  external  stimuli,  and  the  direct 


THEORIES    OF    LAMARCK   AND    DARWIN  385 

inheritance  of  the  same.  His  theory  is  comprehensive, 
so  much  so  that  he  includes  mankind  in  his  general  con- 
clusions. 

Lamarck  supposed  that  an  animal  having  become 
adapted  to  its  surroundings  would  remain  relatively  stable 
as  to  its  structure.  To  the  objection  raised  by  Cuvier  that 
animals  from  Egypt  had  not  changed  since  the  days  when 
they  were  preserved  as  mummies,  he  replied  that  the  climate 
of  Egypt  had  remained  constant  for  centuries,  and  therefore 
no  change  in  its  fauna  was  to  be  expected. 

Species. — Since  the  question  of  the  fixity  of  species  is  the 
central  one  in  theories  of  evolution,  it  will  be  worth  while  to 
quote  Lamarck's  definition  of  species:  "All  those  who  have 
had  much  to  do  with  the  study  of  natural  history  know  that 
naturalists  at  the  present  day  are  extremely  embarrassed  in 
defining  what  they  mean  by  the  word  species.  .  .  .  We  call 
species  every  collection  of  individuals  which  are  alike  or 
almost  so,  and  we  remark  that  the  regeneration  of  these 
individuals  conserves  the  species  and  propagates  it  in  con- 
tinuing successively  to  reproduce  similar  individuals."  He 
then  goes  on  with  a  long  discussion  to  show  that  large  collec- 
tions of  animals  exhibit  a  great  variation  in  species,  and  that 
they  have  no  absolute  stability,  but  "enjoy  only  a  relative 
stabihty." 

Herbert  Spencer  adopted  and  elaborated  the  theory  of 
Lamarck.  He  freed  it  from  some  of  its  chief  crudities,  such 
as  the  idea  of  an  innate  tendency  toward  perfection.  In 
many  controversies  Mr.  Spencer  defended  the  idea  of  the 
transmission  of  acquired  characters.  The  ideas  of  Lamarck 
have,  therefore,  been  transmitted  to  us  largely  in  the  Spence- 
rian  mold  and  in  the  characteristic  language  of  that  great 
philosopher.  There  has  been  but  little  tendency  to  go  to 
Lamarck's  original  writings.  Packard,  whose  biography  of 
Lamarck  appeared  in  igci,  has  made  a  thorough  analysis 


386  BIOLOGY    AND    ITS    MAKERS 

of  his,  writings  and  had  incidentally  corrected  several  erro- 
neous conception. 

Neo-Lamarckism. — The  ideas  of  Lamarck  regarding  the 
beginning  of  variations  have  been  revived  and  accorded  much 
respect  under  the  designation  of  Neo-Lamarckism.  The 
revival  of  Lamarckism  is  especially  owing  to  the  palaeon- 
tological  investigations  of  Cope  and  Hyatt.  The  work  of 
E.  D.  Cope  in  particular  led  him  to  attach  importance  to  the 
effect  of  mechanical  and  other  external  causes  in  producing 
variation,  and  he  points  out  many  instances  of  use-inher- 
itance. Neo-Lamarckism  has  a  considerable  following;  it 
is  a  revival  of  the  fundamental  ideas  of  Lamarck. 

Darwin's  Theory 

While  Lamarck's  theory  rests  upon  two  sets  of  facts, 
Darwin's  is  founded  on  three:  viz.,  the  facts  of  variation, 
of  inheritance,  and  of  natural  selection.  The  central  feature 
of  his  theory  is  the  idea  of  natural  selection.  No  one  else 
save  Wallace  had  seized  upon  this  feature  when  Darwin 
made  it  the  center  of  his  system.  On  account  of  the  part 
taken  by  Wallace  simultaneously  with  Darwin  in  announcing 
natural  selection  as  the  chief  factor  of  evolution,  it  is  appro- 
priate to  designate  this  contribution  as  the  Darwin- Wallace 
principle  of  natural  selection.  The  interesting  connection 
between  the  original  conclusions  of  Darwin  and  Wallace  is 
set  forth  in  Chapter  XIX. 

Variation. — It  will  be  noticed  that  two  of  the  causes 
assigned  by  Darwin  are  the  same  as  those  designated  by  La- 
marck, but  their  treatment  is  quite  different.  Darwin  (Fig. 
1 13)  assumed  variation  among  animals  and  plants  without  at- 
tempting to  account  for  it,  while  Lamarck  undertook  to  state 
the  particular  influences  which  produce  variation,  and  al- 
though we  must  admit  that  Lamarck  was  not  entirely  sue- 


Fig.  113. — Charles  Darwin,  1809-1882. 


S^^  BIOLOGY   AND    ITS    MAKERS 

cessful  in  this  attempt,  the  fact  that  he  undertook  the  task 
places  his  contribution  at  the  outset  on  a  very  high  plane. 

The  existence  of  variation  as  established  by  observation 
is  unquestioned.  No  two  living  organisms  are  exactly  alike 
at  the  time  of  their  birth,  and  even  if  they  are  brought  up 
together  under  identical  surroundings  they  vary.  The  varia- 
tion of  plants  and  animals  under  domestication  is  so  con- 
spicuous and  well  known  that  this  kind  of  variation  was  the 
first  to  attract  attention.  It  was  asserted  that  these  varia- 
tions were  perpetuated  because  the  forms  had  been  protected 
by  man,  and  it  was  doubted  that  animals  varied  to  any  con- 
siderable extent  in  a  state  of  nature.  Extended  collections 
and  observ^ations  in  field  and  forest  have,  however,  set  this 
question  at  rest. 

If  crows  or  robins  or  other  birds  are  collected  on  an  exten- 
sive scale,  the  variability  of  the  same  species  will  be  evident. 
Many  examples  show  that  the  so-called  species  differ  greatly 
in  widely  separated  geographical  areas,  but  collections  from 
the  intermediate  territory  demonstrate  that  the  variations 
are  connected  by  a  series  of  fine  gradations.  If,  for  illustra- 
tion, one  should  pass  across  the  United  States  from  the 
Atlantic  to  the  Pacific  coast,  collecting  one  species  of  bird, 
the  entire  collection  would  exhibit  wide  variations,  but  the 
extremes  would  be  connected  by  intermediate  forms. 

The  amount  of  variation  in  a  state  of  nature  is  much 
greater  than  was  at  first  supposed,  because  extensive  collec- 
tions were  lacking,  but  the  existence  of  wide  variation  is  now 
established  on  the  basis  of  observation.  This  fact  of  varia- 
tion among  animals  and  plants  in  the  state  of  nature  is 
unchallenged,  and  affords  a  good  point  to  start  from  in  con- 
sidering Darwinism. 

Inheritance. — The  idea  that  these  variations  are  inher- 
ited is  the  second  point.  But  what  particular  variations  will 
be   preserved   and   fostered   by   inheritance,    and   on   what 


THEORIES    OF    LAMARCK    AND    DARWIN  389 

principle  they  will  be  selected,  is  another  question — and  a 
notable  one.  Darwin's  reply  was  that  those  variations  which 
are  of  advantage  to  the  individual  will  be  the  particular  ones 
selected  by  nature  for  inheritancig.  While  Darwin  implies 
the  inheritance  of  acquired  characteristics,  his  theory  of 
heredity  was  widely  different  from  that  of  Lamarck.  Dar- 
win's theory  of  heredity,  designated  the  provisional  theory  of 
pangenesis,  has  been  already  considered  (see  Chapter  XIV). 

Natural  Selection. — Since  natural  selection  is  the  main 
feature  of  Darwin's  doctrine,  we  must  devote  more  time  to 
it.  Darwin  frequently  complained  that  very  few  of  his 
critics  took  the  trouble  to  find  out  what  he  meant  by  the  term 
natural  selection.  A  few  illustrations  will  make  his  meaning 
clear.  Let  us  first  think  of  artificial  selection  as  it  is  applied 
by  breeders  of  cattle,  fanciers  of  pigeons  and  of  other  fowls, 
etc.  It  is  well  known  that  by  selecting  particular  variations 
in  animals  and  plants,  even  when  the  variations  are  slight, 
the  breeder  or  the  horticulturalist  will  be  able  in  a  short 
time  to  produce  new  races  of  organic  forms.  This  artificial 
selection  on  the  part  of  man  has  given  rise  to  the  various 
breeds  of  dogs,  the  150  different  kinds  of  pigeons,  etc.,  all 
of  which  breed  true.  The  critical  question  is.  Have  these  all 
an  individual  ancestral  form  in  nature  ?  Observation  shows 
that  many  different  kinds — as  pigeons — may  be  traced  back 
to  a  single  ancestral  form,  and  thus  the  doctrine  of  the  fixity 
of  species  is  overthrown. 

Now,  since  it  is  demonstrated  by  observation  that  varia- 
tions occur,  if  there  be  a  selective  principle  at  work  in 
nature,  effects  similar  to  those  caused  by  artificial  selec- 
tion will  be  produced.  The  selection  by  nature  of  the  forms 
fittest  to  survive  is  what  Darwin  meant  by  natural  selection. 
We  can  never  understand  the  application,  however,  unless 
we  take  into  account  the  fact  that  while  animals  tend  to 
multiply  in  geometrical  progression,  as  a  matter  of  fact  the 


390  BIOLOGY   AND    ITS    MAKERS 

number  of  any  one  kind  remains  practically  constant. 
Although  the  face  of  nature  seems  undisturbed,  there  is 
nevertheless  a  struggle  for  existence  among  all  animals. 

This  is  easily  illustrated  when  we  take  into  account  the 
breeding  of  fishes.  The  trout,  for  illustration,  lays  from  60,000 
to  100,000  eggs.  If  the  majority  of  these  arrived  at  maturitv 
and  gave  rise  to  progeny,  the  next  generation  would  represent 
a  prodigious  number,  and  the  numbers  in  the  succeeding 
generations  would  increase  so  rapidly  that  soon  there  would 
not  be  room  in  the  fresh  waters  of  the  earth  to  contain  their 
descendants.  What  becomes  of  the  immense  number  of 
fishes  that  die  ?  They  fall  a  prey  to  others,  or  they  are  not 
able  to  get  food  in  competition  with  other  more  hardy  rela- 
tives, so  that  it  is  not  a  matter  of  chance  that  determines 
which  ones  shall  survive;  those  which  are  the  strongest,  the 
better  fitted  to  their  surroundings,  are  the  ones  which  will 
be  perpetuated. 

The  recognition  of  this  struggle  for  existence  in  nature, 
and  the  consequent  survival  of  the  fittest,  shows  us  more 
clearly  what  is  meant  by  natural  selection.  Instead  of  man 
making  the  selection  of  those  particular  forms  that  are  to 
survive,  it  is  accomplished  in  the  course  of  nature.  This  is 
natural  selection. 

Various  Aspects  of  Natural  Selection. — Further  illustra- 
tions are  needed  to  give  some  idea  of  the  various  phases  of 
natural  selection.  Speed  in  such  animals  as  antelopes  may 
be  the  particular  thing  which  leads  to  their  protection.  It 
stands  to  reason  that  those  with  the  greatest  speed  would 
escape  more  readily  from  their  enemies,  and  would  be  the 
particular  ones  to  survive,  while  the  weaker  and  slower  ones 
would  fall  victims  to  their  prey.  In  all  kinds  of  strain  due  to 
scarcity  of  food,  inclemency  of  weather,  and  other  untoward 
circumstances,  the  forms  which  are  the  strongest,  physio- 
logically speaking,  will  have  the  best  chance  to  weather  the 


THEORIES    OF    LAMARCK    AND    DARWIN  391 

Strain  and  to  survive.  As  another  illustration,  Darwin 
pointed  out  that  natural  selection  had  produced  a  long-legged 
race  of  prairie  wolves,  while  the  timber  wolves,  which  have 
less  occasion  for  running,  are  short-legged. 

We  can  also  see  the  operation  of  natural  selection  in  the 
production  of  the  sharp  eyes  of  birds  of  prey.  Let  us  con- 
sider the  way  in  which  the  eyes  of  the  hawk  have  beeh  per- 
fected by  evolution.  Natural  selection  compels  the  eye  to 
come  up  to  a  certain  standard.  Those  hawks  that  are  bom 
with  weak  or  defective  vision  cannot  cope  with  the  conditions 
under  which  they  get  their  food.  The  sharp-eyed  forms 
would  be  the  first  to  discern  their  prey,  and  the  most  sure  in 
seizing  upon  it.  Therefore,  those  with  defective  vision  or 
with  vision  that  falls  below  the  standard  will  be  at  a  very 
great  disadvantage.  The  sharp-eyed  forms  will  be  preserved 
by  a  selective  process.  Nature  selects,  we  may  say,  the 
keener-eyed  birds  of  prey  for  survival,  and  it  is  easy  to  see 
that  this  process  of  natural  selection  would  establish  and 
maintain  a  standard  of  vision. 

But  natural  selection  tends  merely  to  adapt  animals  to 
their  surroundings,  and  does  not  always  operate  in  the  direc- 
tion of  increasing  the  efficiency  of  the  organ.  We  take  an- 
other illustration  to  show  how  Darwin  explains  the  origin  of 
races  of  short-winged  beetles  on  certain  oceanic  islands. 
Madeira  and  other  islands,  as  Kerguelen  island  of  the  Indian 
Ocean,  are  among  the  most  windy  places  in  the  world.  The 
strong-winged  beetles,  being  accustomed  to  disport  them- 
selves in  the  air,  would  be  carried  out  to  sea  by  the  sudden 
and  violent  gales  which  sweep  over  those  islands,  while  the 
weaker-winged  forms  would  be  left  to  perpetuate  their  kind. 
Thus,  generation  after  generation,  the  strong-winged  beetles 
would  be  ehminated  by  a  process  of  natural  selection,  and 
there  would  be  left  a  race  of  short-winged  beetles  derived 
from  long-winged  ancestors.     In  this  case  the  organs  are 


392  BIOLOGY   AND    ITS    MAKERS 

reduced  in  their  development,  rather  than  increased;  but 
manifestly  the  short -winged  race  of  beetles  is  better  adapted 
to  Hve  under  the  particular  conditions  that  surround  their 
life  in  these  islands. 

While  this  is  not  a  case  of  increase  in  the  particular  organ, 
it  illustrates  a  progressive  series  of  steps  whereby  the  organ- 
ism becomes  better  adapted  to  its  surroundings.  A  similar 
instance  is  found  in  the  suppression  of  certain  sets  of  organs 
in  internal  parasites.  For  illustration,  the  tapeworm  loses 
particular  organs  of  digestion  for  which  it  does  not  have 
continued  use ;  but  the  reproductive  organs,  upon  which  the 
continuance  of  its  life  depends,  are  greatly  increased.  Such 
cases  as  the  formation  of  short- winged  beetles  show  us  that 
the  action  of  natural  selection  is  not  always  to  preserve  what 
we  should  call  the  best,  but  simply  to  preserve  the  fittest. 
Development,  therefore,  under  the  guidance  of  natural  selec- 
tion is  not  always  progressive.  Selection  by  nature  does 
not  mean  the  formation  and  preservation  of  the  ideally  per- 
fect, but  merely  the  survival  of  those  best  fitted  to  their 
environment. 

Color. — The  various  ways  in  which  natural  selection  acts 
are  exceedingly  diversified.  The  colors  of  animals  may  be 
a  factor  in  their  preservation,  as  the  stripes  on  the  zebra 
tending  to  make  it  inconspicuous  in  its  surroundings.  The 
stripes  upon  the  sides  of  tigers  simulate  the  shadows  cast  by 
the  jungle  grass  in  which  the  animals  live,  and  serve  to  con- 
ceal them  from  their  prey  as  well  as  from  enemies.  Those 
animals  that  assume  a  white  color  in  winter  become  thereby 
less  conspicuous,  and  they  are  protected  by  their  coloration. 

As  further  illustrating  color  as  a  factor  in  the  preserva- 
tion of  animals,  we  may  cite  a  story  originally  told  by 
Professor  E.  S.  Morse.  When  he  was  collecting  shells  on  the 
white  sand  of  the  Japanese  coast,  he  noticed  numerous  white 
tiger-beetles,  which  could  scarcely  be  seen  against  the  white 


THEORIES    OF    LAMARCK    AND    DARWIN  393 

background.  They  could  be  detected  chiefly  by  their 
shadows  when  the  sun  was  shining.  As  he  walked  along 
the  coast  he  came  to  a  wide  band  of  lava  which  had  flowed 
from  a  crater  across  the  intervening  country  and  plunged 
into  the  sea,  leaving  a  broad  dark  band  some  miles  in  breadth 
across  the  white  sandy  beach.  As  he  passed  from  the  white 
sand  to  the  dark  lava,  his  attention  was  attracted  to  a  tiger- 
beetle  almost  identical  with  the  white  one  except  as  to  color. 
Instead  of  being  white,  it  was  black.  He  found  this  broad, 
black  band  of  lava  inhabited  by  the  black  tiger  beetle,  and 
found  very  few,  if  any,  of  the  white  kind.  This  is  a  striking 
illustration  of  what  has  occurred  in  nature.  These  two 
beetles  are  of  the  same  species,  and  in  examining  the  condi- 
tions under  which  they  grow,  it  is  discovered  that  out  of  the 
eggs  laid  by  the  original  white  forms,  there  now  and  then 
appears  one  of  a  dusky  or  black  color.  Consider  how  con- 
spicuous this  dark  object  would  be  against  the  white  back- 
ground of  sand.  It  would  be  an  easy  mark  for  the  birds 
of  prey  that  fly  about,  and  therefore  on  the  white  surface 
the  black  beetles  would  be  destroyed,  while  the  w^hite  ones 
would  be  left.  But  on  the  black  background  of  lava  the 
conditions  are  reversed.  There  the  white  forms  would  be  the 
conspicuous  ones;  as  they  wandered  upon  the  black  surface, 
they  would  be  picked  up  by  birds  of  prey  and  the  black  ones 
would  be  left.  Thus  we  see  another  instance  of  the  operation 
of  natural  selection. 

Mimicry. — We  have,  likewise,  in  nature  a  great  number 
of  cases  that  are  designated  mimicry.  For  illustration,  cer- 
tain caterpillars  assume  a  stiff  position,  resembling  a  twig 
from  a  branch.  We  have  also  leaf-like  butterflies.  The  Kal- 
lima  of  India  is  a  conspicuous  illustration  of  a  butterfly 
having  the  upper  surface  of  its  wings  bright-colored,  and  the 
lower  surface  dull.  When  it  settles  upon  a  twig  the  wings 
are  closed  and  the  under- sides   have  a  mark  across  them 


394  BIOLOGY   AND    ITS    MAKERS 

resembling  the  mid-rib  of  a  leaf,  so  that  the  whole  butterfly 
in  the  resting  position  becomes  inconspicuous,  being  pro- 
tected by  mimicry. 

One  can  readily  see  how  natural  selection  would  be  evoked 
in  order  to  explain  this  condition  of  affairs.  Those  forms 
that  varied  in  the  direction  of  looking  like  a  leaf  would  be 
the  most  perfectly  protected,  and  this  feature  being  fostered 
by  natural  selection,  would,  in  the  course  of  time,  produce  a 
race  of  butterflies  the  resemblance  of  whose  folded  wings  to 
a  leaf  would  serve  as  a  protection  from  enemies. 

It  may  not  be  out  of  place  to  remind  the  reader  that  the 
illustrations  cited  are  introduced  merely  to  elucidate  Dar- 
win's theory  and  the  writer  is  not  committed  to  accepting 
them  as  explanations  of  the  phenomena  involved.  He  is 
not  unmindful  of  the  force  of  the  criticisms  against  the  ade- 
quacy of  natural  selection  to  explain  the  evolution  of  all 
kinds  of  organic  structures. 

Many  other  instances  of  the  action  of  color  might  be 
added,  such  as  the  wearing  of  warning  colors,  those  colors 
which  belong  to  butterflies,  grubs,  and  other  animals  that 
have  a  noxious  taste.  These  warning  colors  have  taught 
birds  to  leave  alone  the  forms  possessing  those  colors.  Some- 
times forms  which  do  not  possess  a  disagreeable  taste 
secure  protection  by  mimicking  the  colors  of  the  noxious 
varieties. 

Sexual  Selection. — There  is  an  entirely  different  set  of 
cases  which  at  first  sight  would  seem  difficult  to  explain  on 
the  principle  of  selection.  How,  for  instance,  could  we 
explain  the  feathers  in  the  tails  of  the  birds  of  paradise,  or 
that  peculiar  arrangement  of  feathers  in  the  tail  of  the  lyre- 
bird, or  the  gorgeous  display  of  tail-feathers  of  the  male 
peacock?  Here  Mr.  Darwin  seized  upon  a  selective  prin- 
ciple arising  from  the  influence  of  mating.  The  male  birds 
in  becoming  suitors  for  a  particular  female  have  been  accus- 


THEORIES    OF    LAMARCK   AND    DARWIN  395 

tomed  to  display  their  tail-feathers;  the  one  with  the  most 
attractive  display  excites  the  pairing  instinct  in  the  highest 
degree,  and  becomes  the  selected  suitor.  In  this  way, 
through  the  operation  of  a  form  of  selection  which  Darwin 
designates  sexual  selection,  possibly  such  curious  adaptations 
as  the  peacock's  tail  may  be  accounted  for. 

It  should  be  pointed  out  that  this  part  of  the  theory  is 
almost  wholly  discredited  by  biologists.  Experimental  evi- 
dence is  against  it.  Nevertheless  in  a  descriptive  account 
of  Darwin's  theory  it  may  be  allowed  to  stand  without 
critical  comment. 

Inadequacy  of  Natural  Selection. — In  nature,  under  the 
struggle  for  existence,  the  fittest  will  be  preserved;  and  natural 
selection  will  operate  toward  the  elaboration  or  the  suppres- 
sion of  certain  organs  or  certain  characteristics  when  the  elab- 
oration or  the  suppression  is  of  advantage  to  the  animal  form. 
Much  has  been  said  of  ]ate  as  to  the  inadequacy  of  natural 
selection.  Herbert  Spencer  and  Huxley,  both  accepting 
natural  selection  as  one  of  the  factors,  doubted  its  complete 
adequacy. 

One  point  is  often  overlooked,  and  should  be  brought  out 
with  clearness;  viz.,  that  Darwin  himself  was  the  first  to 
point  out  clearly  the  inadequacy  of  natural  selection  as  a 
universal  law  for  the  production  of  the  great  variety  of 
animals  and  plants.  In  the  second  edition  of  the  Origin  of 
Species  he  says:  "But,  as  my  conclusions  have  lately  been 
much  misrepresented,  and  it  has  been  stated  that  I  attribute 
the  modification  of  species  exclusively  to  natural  selection, 
I  may  be  permitted  to  remark  that  in  the  first  edition  of  this 
work  and  subsequently  I  placed  in  a  most  conspicuous 
position, — namely,  at  the  close  of  the  introduction — the  follow- 
ing words:  'I  am  convinced  that  natural  selection  has  been 
the  main,  but  not  the  exclusive  means  of  modification.'  This 
has  been  of  no  avail.     Great  is  the  power  of  steady  mis- 


396  BIOLOGY   AND    ITS    MAKERS 

representation.  But  the  history  of  science  shows  that  for- 
tunately this  power  does  not  long  endure." 

The  reaction  against  the  all-sufficiency  of  natural  selec- 
tion, therefore,  is  something  which  was  anticipated  by  Dar- 
win, and  the  quotation  made  above  will  be  a  novelty  to  many 
of  our  readers  who  supposed  that  they  understood  Darwin's 
position. 

Confusion  between  Lamarck's  and  Darwin's  Theories. — 
Besides  the  failure  to  understand  what  Darwin  has  written, 
there  is  great  confusion,  both  in  pictures  and  in  writings,  in 
reference  to  the  theories  of  Darwin  and  Lamarck.  Poulton 
illustrated  a  state  of  confusion  in  one  of  his  lectures  on  the 
theory  of  organic  evolution,  and  the  following  instances  are 
quoted  from  memory. 

We  are  most  of  us  familiar  with  such  pictures  as  the 
following:  A  man  standing  and  waving  his  arms;  in  the  next 
picture  these  arms  and  hands  become  enlarged,  and  in  the 
successive  pictures  they  undergo  transformations  into  wings, 
and  the  transference  is  made  into  a  flying  animal. 

Such  pictures  are  designated  ''The  origin  of  flight  after 
Darwin."  The  interesting  circumstance  is  this,  that  the 
iUustration  does  not  apply  to  Darwin's  idea  of  natural  selec- 
tion at  all,  but  is  pure  Lamarckism.  Lamarck  contended 
for  the  production  of  new  organs  through  the  influence  of 
use  and  disuse,  and  this  particular  illustration  refers  to  that, 
and  not  to  natural  selection  at  all. 

Among  the  examples  of  ridicule  to  which  Darwin's  ideas 
have  been  exposed,  we  cite  one  verse  from  the  song  of  Lord 
Neaves.  His  lordship  wrote  a  song  with  a  large  number  of 
verses  hitting  off  in  jocular  vein  many  of  the  claims  and 
foibles  of  his  time.  In  attempting  to  make  fun  of  Darwin's 
idea  he  misses  completely  the  idea  of  natural  selection,  but 
hits  upon  the  principle  enunciated  by  Lamarck,  instead. 
He  says: 


THEORIES    OF    LAMARCK    AND    DARWIN  397 

"A  deer  with  a  neck  which  was  longer  by  half 
Than  the  rest  of  his  family's — try  not  to  laugh — 
By  stretching  and  stretching  became  a  giraffe, 
Which  nobody  can  deny." 

The  clever  young  woman,  Miss  Kendall,  however,  in  her 
Song  oj  the  Ichthyosaurus,  showed  clearness  in  grasping 
Darwin's  idea  when  she  wrote: 

"Ere  man  was  developed,  our  brother, 
We  swam,  we  ducked,  and  we  dived, 
And  we  dined,  as  a  rule,  on  each  other. 
What  matter?     The  toughest  survived." 

This  hits  the  idea  of  natural  selection.  The  other  two  illus- 
trations miss  it,  but  strike  the  principle  which  was  enunciated 
by  Lamarck.  This  confusion  between  Lamarckism  and  Dar- 
winism is  very  wide-spread. 

Darwin's  book  on  the  Origin  oj  Species,  published  in 
1859,  was  epoch-making.  If  a  group  of  scholars  were  asked 
to  designate  the  greatest  book  of  the  nineteenth  century — 
that  is,  the  book  which  created  the  greatest  intellectual  stir — 
it  is  likely  that  a  large  proportion  of  them  would  reply  that 
it  is  Darwin's  Origin  of  Species.  Its  influence  was  so  great 
in  the  different  domains  of  thought  that  we  may  observe  a 
natural  cleavage  between  the  thought  in  reference  to  nature 
between  1859  and  all  preceding  time.  His  other  less  widely 
known  books  on  Animals  and  Plants  Under  Domestication, 
the  Descent  0}  Man,  etc.,  etc.,  are  also  important  contributions 
to  the  discussion  of  his  theory.  A  brief  account  of  Darwin, 
the  man,  will  be  found  in  Chapter  XIX. 


CHAPTER  XVIII 

THEORIES   OF  EVOLUTION   CONTINUED: 
WEISMANN,  DE  VRIES 

Weism Ann's  views  have  passed  through  various  stages  of 
remodeHng  since  his  first  pubhc  championship  of  the  Theory 
of  Descent  on  assuming,  in  1867,  the  position  of  professor  of 
zoology  in  the  University  of  Freiburg.  Some  time  after  that 
date  he  originated  his  now  famous  theory  of  heredity,  which 
has  been  retouched,  from  time  to  time,  as  the  resuh  of 
aggressive  criticism  from  others,  and  the  expansion  of  his 
own  mental  horizon.  As  he  said  in  1904,  regarding  his 
lectures  on  evolution  which  have  been  delivered  almost  reg- 
ularly every  year  since  1880,  they  "were  gradually  modified 
in  accordance  with  the  state  of  my  knowledge  at  the  time, 
so  that  they  have  been,  I  may  say,  a  mirror  of  my  own  intel- 
lectual evolution." 

Passing  over  his  book.  The  Germ  Plasm,  published  in 
English  in  1893,  we  may  fairly  take  his  last  book.  The 
Evolution  Theory,  1904,  as  the  best  exposition  of  his  con- 
clusions. The  theoretical  views  of  Weismann  have  been 
the  field  of  so  much  strenuous  controversy  that  it  will  be  well 
perhaps  to  take  note  of  the  spirit  in  which  they  have  been 
presented.  In  the  preface  of  his  book  just  mentioned,  he 
says:  "I  make  this  attempt  to  sum  up  and  present  as  a  har- 
monious whole  the  theories  which  for  forty  years  I  have  been 
gradually  building  up  on  the  basis  of  the  legacy  of  the  great 
workers  of  the  past,  and  on  the  results  of  my  own  investiga- 

398 


THEORIES    OF    WEISMANN    AND    DE    VRIES       399 

tions  and  those  of  my  fellow-workers,  not  because  I  regard 
the  picture  as  incomplete  or  incapable  of  improvement,  but 
because  I  believe  its  essential  features  to  be  correct,  and 
because  an  eye-trouble  which  has  hindered  my  work  for 
many  years  makes  it  uncertain  whether  I  shall  have  much 
more  time  and  strength  granted  to  me  for  its  further  elabora- 
tion." 

The  germ-plasm  theory  is  primarily  a  theory  of  heredity, 
and  only  when  connected  with  other  considerations  does  it 
become  the  full-fledged  theory  of  evolution  known  as  Weis- 
mannism.  The  theory  as  a  whole  involves  so  many  intricate 
details  that  it  is  difficult  to  make  a  clear  statement  of  it  for 
general  readers.  If  in  considering  the  theories  of  Lamarck 
and  Darwin  it  was  found  advantageous  to  confine  attention 
to  salient  points  and  to  omit  details,  it  is  all  the  more  essential 
to  do  so  in  the  discussion  of  Weismann's  theory. 

In  his  prefatory  note  to  the  Enghsh  edition  of  The 
Evolution  Theory  Thomson,  the  translator,  summarizes  Weis- 
mann's especial  contributions  as:  ''  (i)  the  illumination  of  the 
evolution  process  with  a  wealth  of  fresh  illustrations;  (2) 
the  vindication  of  the  'germ-plasm'  concept  as  a  valuable 
working  hypothesis;  (3)  the  final  abandonment  of  any 
assumption  of  transmissible  acquired  characters;  (4)  a 
further  analysis  of  the  nature  and  origin  of  variations;  and 
(5),  above  all,  an  extension  of  the  selection  principle  of 
Darwin  and  Wallace,  which  finds  its  logical  outcome  in  the 
suggestive  theory  of  germinal  selection." 

Continuity  of  the  Germ-Plasm. — Weismann's  theory  is 
designated  that  of  continuity  of  the  germ-plasm,  and  in  con- 
sidering it  we  must  first  give  attention  to  his  conception  of 
the  germ-plasm.  As  is  well  known,  animals  and  plants 
spring  from  germinal  elements  of  microscopic  size;  these  are, 
in  plants,  the  spores,  the  seeds,  and  their  fertilizing  agents; 
and,  in  animals,  the  eggs  and  the  sperms.     Now,  since  all 


400  BIOLOGY   ANY   ITS    MAKERS 

animals,  even  the  highest  developed,  begin  in  a  fertilized  egg, 
that  structure,  minute  as  it  is,  must  contain  all  hereditary 
qualities,  since  it  is  the  only  material  substance  that  passes 
from  one  generation  to  another.  This  hereditary  substance 
is  the  germ-plasm.  It  is  the  living,  vital  substance  of  organ- 
isms that  takes  part  in  the  development  of  new  generations. 

Naturalists  are  agreed  on  this  point,  that  the  more  com- 
plex animals  and  plants  have  been  derived  from  the  simpler 
ones;  and,  this  being  accepted,  the  attention  should  be  fixed 
on  the  nature  of  the  connection  between  generations  during 
their  long  line  of  descent.  In  the  reproduction  of  single- 
celled  organisms,  the  substance  of  the  entire  body  is  divided 
during  the  transmission  of  life,  and  the  problem  both  of 
heredity  and  origin  is  relatively  simple.  It  is  clear  that  in 
these  single-celled  creatures  there  is  unbroken  continuity  of 
body-substance  from  generation  to  generation.  But  in  the 
higher  animals  only  a  minute  portion  of  the  organism  is 
passed  along. 

Weismann  points  out  that  the  many-celled  body  was 
gradually  produced  by  evolution;  and  that  in  the  trans- 
mission of  life  by  the  higher  animals  the  continuity  is  not 
between  body-cells  and  their  like,  but  only  between  ger- 
minal elements  around  which  in  due  course  new  body-cells 
are  developed.  Thus  he  regards  the  body-cells  as  constitut- 
ing a  sort  of  vehicle  within  which  the  germ-cells  are  carried. 
The  germinal  elements  represent  the  primordial  substance 
around  which  the  body  has  been  developed,  and  since  in  all 
the  long  process  of  evolution  the  germinal  elements  have  been 
the  only  form  of  connection  between  different  generations, 
they  have  an  unbroken  continuity. 

This  conception  of  the  continuity  of  the  germ-plasm  is 
the  foundation  of  Weismann' s  doctrine.  As  indicated  before, 
the  general  way  in  which  he  accounts  for  heredity  is  that  the 
offspring  is  like  the  parent  because  it  is  composed  of  some  of 


THEORIES    OF    WEISMANN    AND    DE    VRIES       401 

the  same  stuff.  The  rise  of  the  idea  of  germinal  continuity 
has  been  indicated  in  Chapter  XIV,  where  it  was  pointed  out 
that  Weismann  was  not  the  originator  of  the  idea,  but  he  is  nev- 
ertheless the  one  who  has  developed  it  the  most  extensively. 

Complexity  of  the  Germ-Plasm. — The  germ-plasm  has 
been  molded  for  so  many  centuries  by  external  circum- 
stances that  it  has  acquired  an  organization  of  great  com- 
plexity. This  appears  from  the  following  considerations: 
Protoplasm  is  impressionable;  in  fact,  its  most  characteristic 
feature  is  that  it  responds  to  stimulation  and  modifies  itself 
accordingly.  These  subtle  changes  occurring  within  the 
protoplasm  affect  its  organization,  and  in  the  long  run  it  is 
the  summation  of  experiences  that  determines  what  the  pro- 
toplasm shall  be  and  how  it  will  behave  in  development. 
Two  masses  of  protoplasm  differ  in  capabilities  and  poten- 
tialities according  to  the  experiences  through  which  they  have 
passed,  and  no  two  will  be  absolutely  identical.  All  the  time 
the  body  was  being  evolved  the  protoplasm  of  the  germinal 
elements  was  being  molded  and  changed,  and  these  ele- 
ments therefore  possess  an  inherited  orgnization  of  great 
complexity. 

When  the  body  is  built  anew  from  the  germinal  ele- 
ments, the  derived  qualities  come  into  play,  and  the  whole 
process  is  a  succession  of  responses  to  stimulation.  This  is 
in  a  sense,  on  the  part  of  the  protoplasm,  a  repeating  of  its 
historical  experience.  In  building  the  organism  it  does  not 
go  over  the  ground  for  the  first  time,  but  repeats  the  activities 
which  it  took  centuries  to  acquire. 

The  evident  complexity  of  the  germ-plasm  made  it 
necessary  for  Weismann,  in  attempting  to  explain  inheritance 
in  detail,  to  assume  the  existence  of  distinct  vital  units  within 
the  protoplasm  of  the  germinal  elements.  He  has  invented 
names  for  these  particular  units  as  biophors,  the  elementary 
vital  units,  and  their  combination  into  determinants,  the 


402  BIOLOGY   AND    ITS    MAKERS 

latter  being  united  into  ids,  idants,  etc.  The  way  in  which 
he  assumes  the  interactions  of  these  units  gives  to  his  theory 
a  highly  speculative  character.  The  conception  of  the 
complex  organization  of  the  germ-plasm  which  Weismann 
reached  on  theoretical  grounds  is  now  being  established  on 
the  basis  of  observation  (see  Chapter  XIV,  p.  313). 

The  Origin  of  Variations. — The  way  in  which  Weismann 
accounts  for  the  origin  of  variation  among  higher  animals 
is  both  ingenious  and  interesting.  In  all  higher  organisms 
the  sexes  are  separate,  and  the  reproduction  of  their  kind  is 
a  sexual  process.  The  germinal  elements  involved  are  seeds 
and  pollen,  eggs  and  sperms.  In  animals  the  egg  bears  all 
the  hereditary  qualities  from  the  maternal  side,  and  the 
sperm  those  from  the  paternal  side.  The  intimate  mixture 
of  these  in  fertilization  gives  great  possibilities  of  variations 
arising  from  the  different  combinations  and  permutations  of 
the  vital  units  within  the  germ-plasm. 

This  union  of  two  germ-plasms  Weismann  calls  amphi- 
mixis, and  for  a  long  time  he  maintaine  1  that  the  purpose 
of  sexual  reproduction  in  nature  is  to  give  origin  to  varia- 
tions. Later  he  extended  his  idea  to  include  a  selection, 
mainly  on  the  basis  of  nutrition,  among  the  vital  elements 
composing  the  germ-plasm.  This  is  germinal  selection, 
which  aids  in  the  production  of  variations. 

In  The  Evolution  Theory,  volume  II,  page  196,  he  says: 
"Now  that  I  understand  these  processes  more  clearly,  my 
opinion  is  that  the  roots  of  all  heritable  variation  lie  in  the 
germ-plasm;  and,  furthermore,  that  the  determinants  are 
continually  oscillating  hither  and  thither  in  response  to 
very  minute  nutritive  changes  and  are  readily  compelled 
to  variation  in  a  definite  direction,  which  may  ultimately  lead 
to  considerable  variations  in  the  structure  of  the  species,  if 
they  are  favored  by  personal  selection,  or  at  least  if  they  are 
not  suppressed  by  it  as  prejudicial." 


HEORIES    OF    WEISMANN    AND    DE    VRIES       403 

But  while  sexual  reproduction  may  be  evoked  to  explain 
the  origin  of  variation  in  higher  animals,  Weismann  thought 
it  was  not  applicable  to  the  lower  ones,  and  he  found  himself 
driven  to  assume  that  variation  in  single-celled  organisms  is 
owing  to  the  direct  influence  of  environment  upon  them, 
and  thus  he  had  an  awkward  assumption  of  variations  arising 
in  a  different  manner  in  the  higher  and  in  the  simplest  organ- 
isms. If  I  correctly  understand  his  present  position,  the 
conception  of  variation  as  due  to  the  direct  influence  of 
environment  is  being  surrendered  in  favor  of  the  action  of 
germinal  selection  among  the  simplest  organisms. 

Extension  of  the  Principle  of  Natural  Selection. — These 
variations,  once  started,  will  be  fostered  by  natural  selection 
provided  they  are  of  advantage  to  the  organism  in  its  struggle 
for  existence.  It  should  be  pointed  out  that  Weismann  is  a 
consistent  Darwinian;  he  not  only  adopts  the  principle  of 
natural  selection,  but  he  extends  the  field  of  its  operation 
from  externals  to  the  internal  parts  of  the  germinal  elements. 

"Roux  and  others  have  elaborated  the  idea  of  a  struggle 
of  the  parts  within  the  organism,  and  of  a  corresponding 
intra-selection ;  .  .  .  but  Weismann,  after  his  manner,  has 
carried  the  selection-idea  a  step  farther,  and  has  pictured 
the  struggle  among  the  determining  elements  of  the  germ- 
cell's  organization.  It  is  at  least  conceivable  that  the  stronger 
'determinants,'  i.e.,  the  particles  embodying  the  rudiments 
of  certain  qualities,  will  make  more  of  the  food-supply  than 
those  which  are  weaker,  and  that  a  selective  process  will 
ensue"  (Thomson).  This  is  the  conception  of  germinal 
selection. 

He  has  also  extended  the  application  of  the  general 
doctrine  of  natural  selection  by  supplying  a  great  number 
of  new  illustrations. 

The  whole  theory  of  Weismann  is  so  well  constructed 
that  it  is  very  alluring.     Each  successive  position  is  worked 


404  BIOLOGY   AND    ITS    MAKERS 

out  with  such  detail  and  apt  illustration  that  if  one  follows 
him  step  by  step  without  dissent  on  some  fundamental  prin- 
ciple, his  conclusion  seems  justified.  As  a  system  it  has 
been  elaborated  until  it  makes  a  coherent  appeal  to  the 
intellect. 

Inheritance  of  Acquired  Characters. — Another  funda- 
mental point  in  Weismann's  theory  is  the  denial  that  acquired 
characters  are  transmitted  from  parent  to  offspring.  Prob- 
ably the  best  single  discussion  of  this  subject  is  contained 
in  his  book  on  The  Evolution  Theory,  1904,  to  which  readers 
are  referred. 

A  few  illustrations  will  be  in  place.  Acquired  characters 
are  any  acquisitions  made  by  the  body-cells  during  the 
lifetime  of  an  individual.  They  may  be  obvious,  as  skill 
in  piano-playing,  bicycle-riding,  etc.;  or  they  may  be  very 
recondite,  as  turns  of  the  intellect,  acquired  beliefs,  etc. 
Acquired  bodily  characters  may  be  forcibly  impressed  upon 
the  organism,  as  the  facial  mutilations  practiced  by  certain 
savage  tribes,  the  docking  of  the  tails  of  horses,  of  dogs,  etc. 
The  question  is.  Are  any  acquired  characters,  physical  or 
mental,  transmitted  by  inheritance? 

Manifestly,  it  will  be  difficult  to  determine  on  a  scientific 
basis  whether  or  not  such  qualities  are  inheritable.  One 
would  naturally  think  first  of  applying  the  test  of  experiment 
to  supposed  cases  of  such  inheritances,  and  this  is  the  best 
ground  to  proceed  on. 

It  has  been  maintained  on  the  basis  of  the  classical 
experiments  of  Brown-Sequard  on  guinea-pigs  that  induced 
epilepsy  is  transmitted  to  offspring;  and,  also,  on  the  basis 
of  general  observations,  that  certain  bodily  mutilations  are 
inherited.  Weismann's  analysis  of  the  whole  situation  is 
very  incisive.  He  experimented  by  cutting  off  the  tails  of 
both  parents  of  breeding  mice.  The  experiments  were 
carried  through  twenty-two  generations,  both  parents  being 


THEORIES    OF    WEISMANN    AND    DE    VRIES       405 

deprived  of  their  tails,  without  yielding  any  evidence  that 
the  mutilations  were  inheritable. 

To  take  one  other  case  that  is  less  superficial,  it  is  gener- 
ally believed  that  the  thirst  for  alcoholic  liquors  has  been 
transmitted  to  the  children  of  drunkards,  and  while  Weismann 
admits  the  possibility  of  this,  he  maintains  that  it  is  owing 
to  the  germinal  elements  being  exposed  to  the  influence  of 
the  alcohol  circulating  in  the  blood  of  the  parent  or  parents; 
and  if  this  be  the  case  it  would  not  be  the  inheritance  of  an 
acquired  character,  but  the  response  of  the  organism  to  a 
drug  producing  directly  a  variation  in  the  germ-plasm. 

Notwithstanding  the  well-defined  opposition  of  Weismann, 
the  inheritance  of  acquired  characters  is  still  a  mooted  ques- 
tion. Herbert  Spencer  argued  in  favor  of  it,  and  during  his 
lifetime  had  many  a  pointed  controversy  with  Weismann. 
Eimer  stands  unalterably  against  Weismann' s  position,  and 
the  Neo-Lamarckians  stand  for  the  direct  inheritance  of  use- 
ful variations  in  bodily  structure.  The  question  is  still 
undetermined  and  is  open  to  experimental  observation.  In 
its  present  state  there  are  competent  observers  maintaining 
both  sides,  but  it  must  be  confessed  that  there  is  not  a  single 
case  in  which  the  supposed  inheritance  of  an  acquired  char- 
acter has  stood  the  test  of  critical  examination. 

The  basis  of  Weismann' s  argument  is  not  difficult  to 
understand.  Acquired  characters  affect  the  body-cells,  and 
according  to  his  view  the  latter  are  simply  a  vehicle  for  the 
germinal  elements,  which  are  the  only  things  concerned  in 
the  transmission  of  hereditary  qualities.  Inheritance,  there- 
fore, must  come  through  alterations  in  the  germ-plasm,  and 
not  directly  through  changes  in  the  body-cells. 

Weismann,  the  Man. — The  man  who  for  more  than  forty 
years  elaborated  and  strengthened  this  theory  has  recently 
(Nov.  1914)  passed  away  at  Freiburg.  August  Weismann 
(Fig.  114)  was  born  at  Frankfort-on-the-Main  in  1834.    He 


4o6 


BIOLOGY    AND    ITS    MAKERS 


was  graduated  at  Gottingen  in  1856,  and  for  a  short  time 
thereafter  engaged  in  the  practice  of  medicine.  This  hne  of 
activity  did  not,  however,  satisfy  his  nature,  and  he  turned 
to  the  pursuit  of  microscopic  investigations  in  embryology 


Fig.  114.— August  Weismann,  1834- 19 14. 

and  morphology,  being  encouraged  in  this  work  by  Leuckart, 
whose  name  we  have  already  met  in  this  history.  In  1863 
he  settled  in  Freiburg  as  privat-docent,  and,  in  1867,  was 
promoted  to  a  professorship  and  taught  in  the  department  of 


THEORIES  OF  WEISMANN  AND   DE   VRIES  407 

zoology,  until  his  retirement  a  few  years  before  his  death. 
He  has  made  his  department  famous,  especially  by  his  lec- 
tures on  the  theory  of  descent. 

He  was  a  forceful  and  interesting  lecturer.  One  of  his 
hearers  in  1896  wrote:  "His  lecture-room  is  always  full,  and 
his  popularity  among  his  students  fully  equals  his  fame 
among  scientists." 

It  is  quite  generally  known  that  Weismann  since  he  reached 
the  age  of  thirty  was  afflicted  with  an  eye-trouble,  but  the 
inference  sometimes  made  by  those  unacquainted  with 
his  work  as  an  investigator,  that  he  was  obliged  to  forego 
practical  work  in  the  field  in  which  he  speculated,  is  wrong. 
At  intervals  his  eyes  strengthened  so  that  he  was  able  to 
apply  himself  to  microscopic  observations,  and  he  has  a 
distinguished  record  as  an  observer.  In  embryology 
his  studies  on  the  development  of  the  diptera,  and  of 
the  eggs  of  daphnid  Crustacea,  are  well  known,  as  are  also 
his  observations  on  variations  in  butterflies  and  other 
arthropods. 

He  was  an  accomplished  musician,  and  during  the  period 
of  his  enforced  inactivity  in  scientific  work  he  found  much 
solace  in  playing  "sl  good  deal  of  music."  *'His  continuous 
eye  trouble  must  have  been  a  terrible  obstacle,  but  may  have 
been  the  prime  cause  of  turning  him  to  the  theories  with 
which  his  name  is  connected." 

In  a  short  autobiography  published  in  The  Lamp  in  1903, 
although  written  several  years  earlier,  he  gives  a  glimpse  of 
his  family  life.  "During  the  ten  years  (1864-1874)  of  my 
enforced  inactivity  and  rest  occurred  my  marriage  with 
Fraulein  Marie  Gruber,  who  became  the  mother  of  my 
children  and  was  my  true  companion  for  twenty  years,  until 
her  death.  Of  her  now  I  think  only  with  love  and  gratitude. 
She  was  the  one  who,  more  than  any  one  else,  helped  me 
through  the  gloom  of  this  period.     She  read  much  to  me 


4o8  BIOLOGY   AND    ITS    MAKERS 

at  this  time,  for  she  read  aloud  excellently,  and  she  not  only 
took  an  interest  in  my  theoretical  and  experimental  work, 
but  she  also  gave  practical  assistance  in  it." 

In  1893  h^  published  The  Germ-Plasm,  A  Theory  of 
Heredity,  a  treatise  which  elicited  much  discussion.  From 
that  time  on  he  has  been  actively  engaged  in  replying  to  his 
critics  and  in  perfecting  his  system  of  thought. 

The  Mutation-Theory  of  De  Vries.— Hugo  de  Vries 
(Fig.  115),  director  of  the  Botanical  Garden  in  Amsterdam, 
has  experimented  widely  with  plants,  especially  the  evening 
primrose  (CEnothera  Lamarckiana) ,  and  has  shown  that  dif- 
ferent species  appear  to  rise  suddenly.  The  sudden  variations 
that  breed  true,  and  thus  give  rise  to  new  forms,  he  calls  mu- 
tations, and  this  indicates  the  source  of  the  name  applied  to 
his  theory. 

In  his  i^i^  Mutationstheorie,  published  in  1901,  he  argues 
for  the  recognition  of  mutations  as  the  universal  source  of 
the  origin  of  species.  Although  he  evokes  natural  selection 
for  the  perpetuation  and  improvement  of  variations,  and 
points  out  that  his  theory  is  not  antagonistic  to  that  of  natural 
selection,  it  is  nevertheless  directly  at  variance  with  Darwin's 
fundamental  conception — that  slight  individual  variations 
"  are  probably  the  sole  differences  which  are  effective  in  the 
production  of  new  species"  and  that  "as  natural  selection 
acts  solely  by  accumulating  sUght,  successive,  favorable 
variations,  it  can  produce  no  great  or  sudden  modifications." 
The  foundation  of  De  Vries's  theory  is  that  "species  have 
not  arisen  through  gradual  selection,  continued  for  hundreds 
or  thousands  of  years,  but  by  jumps  through  sudden,  through 
small  transformations."     (Whitman's  translation.) 

The  work  of  De  Vries  is  a  most  important  contribution 
to  the  study  of  the  origin  of  species,  and  is  indicative  of  the 
fact  that  many  factors  must  be  taken  into  consideration  when 
one  attempts  to  analyze  the  process  of  organic  evolution. 
One  great  value  of  his  work  is  that  it  is  based  on  experiments, 


THEORIES    OF    WEISMANN    AND    DE    VRIES       409 

and  that  it  has  given  a  great  stimulus  to  experimental  studies. 
Experiment  was  likewise  a  dominant  feature  in  Darwin's 
work,  but  that  seems  to  have  been  almost  overlooked  in 
the  discussions  aroused  by  his  conclusions;  De  Vries,  by 
building  upon  experimental  evidence,  has  led  naturalists  to 


Fig.   115. — Hugo  de  Vries. 


realize  that  the  method  of  evolution  is  not  a  subject  for 
argumentative  discussion,  but  for  experimental  investigation. 
This  is  most  commendable. 

De  Vries's  theory  tends  also  to  widen  the  field  of  explo- 
ration. Davenport,  Tower,  and  others  have  made  it  clear 
that  species  may  arise  by  slow  accumulations  of  trivial  varia- 
tions, and  that,  while  the  formation  of  species  by  mutation 


4IO  BIOLOGY   AND    ITS   MAKERS 

may  be  admitted,  there  is  still  abundant  evidence  of  evolu- 
tion without  mutation. 

Reconciliation  of  Different  Theories. — All  this  is  leading 
to  a  clearer  appreciation  of  the  points  involved  in  the  dis- 
cussion of  the  theories  of  evolution;  the  tendency  is  not  for 
the  breach  between  the  different  theories  to  be  widened,  but 
for  evolutionists  to  realize  more  fully  the  great  complexity 
of  the  process  they  are  trying  to  explain,  and  to  see  that  no 
single  factor  can  carry  the  burden  of  an  explanation.  Muta- 
tion introduces  a  new  factor  of  species-forming,  but  calls  in 
natural  selection  to  improve  the  variations  arising  by  muta- 
tions. Weismann's  suggestion  of  amphimixis,  to  explain  the 
origin  of  variations,  and  his  extension  of  the  principle  of 
selection  to  the  germinal  elements,  is  distinctly  auxiliary  to 
the  theory  of  natural  selection  and  Lamarck's  contribution 
towards  explaining  the  sources  of  variation  is  also  supple- 
mental. Thus  we  may  look  forward  to  a  reconcihation  be- 
tween apparently  conflicting  views,  and  one  conviction  that 
is  looming  into  prominence  is  that  this  will  be  promoted  by 
less  argument  and  more  experimental  observation. 

That  the  solution  of  the  underlying  question  in  evolution 
will  still  require  a  long  time  is  evident;  as  Whitman  said 
in  his  address  before  the  Congress  of  Arts  and  Science  in 
St.  Louis  in  1904:  **The  problem  of  problems  in  biology 
to-day,  the  problem  which  promises  to  sweep  through  the 
present  century  as  it  has  the  past  one,  with  cumulative  inter- 
est and  correspondingly  important  results,  is  the  one  which 
became  the  life-work  of  Charles  Darwin,  and  which  can  not 
be  better  or  more  simply  expressed  than  in  the  title  of  his 
epoch-making  book,  The  Origin  oj  Specie s."" 

Summary. — The  number  of  points  involved  in  the  four 
theories  considered  above  is  likely  to  be  rather  confusing, 


THEORIES  OF  WEISMANN  AND  DE  VRIES  411 

and  we  may  now  bring  them  into  close  juxtaposition.    The 
salient  features  of  these  theories  are  as  follows: 
I.  Lamarck's  Theory  of  Evolution. 

1.  Variation  is  explained  on  the  principle  of  use  and 

disuse. 

2.  Heredity:  The  variations  are  inherited  directly  and 

improved  in  succeeding  generations. 
A  long  time  and  favorable  conditions  are  required 
for  the  production  of  new  species. 
II.  Darwin's  Theory  of  Natural  Selection. 

1.  Variations  assumed. 

2.  Heredity:  Those  slight  variations  which  are  of  use 

to  the  organism  will  be  perpetuated  by  inher- 
itance. 

3.  Natural  selection  is  the  distinguishing   feature  of 

the  theory.  Through  the  struggle  for  existence 
nature  selects  those  best  fitted  to  survive.  The 
selection  of  trivial  variations  that  are  of  advantage 
to  the  organism,  and  their  gradual  improvement, 
leads  to  the  production  of  new  species. 
IIL   Weismann's  Theory  of  Continuity  of  the  Germ-plasm.' 

1.  The  germ-plasm  has  had  unbroken  continuity  from 

the  beginning  of  life.  Owing  to  its  impression- 
able nature,  it  has  an  inherited  organization  of 
great  complexity. 

2.  Heredity  is  accounted  for  on  the  principle  that  the 

offspring  is  composed  of  some  of  the  same  stuff 
as  its  parents.  The  body-cells  are  not  inherited, 
i.e., 

3.  There  is  no  inheritance  of  acquired  characters. 

4.  Variations  arise  from  the  union  of  the  germinal 

elements,  giving  rise  to  varied  combinations  and 
permutations  of  the  qualities  of  the  germ-plasm. 
The  purpose  of  amphimixis  is  to  give  rise  to  vari- 


412  BIOLOGY  AND  ITS  MAKERS 

ations.    The  direct  influence  of  environment  has 
produced  variations  in  unicellular  organism. 
5.  Weismann   adopts   and   extends   the   principle   of 
natural  selection.    Germinal  selection  is  exhibited 
in  the  germ-plasm. 
IV.    De  Vries's  Theory  of  Mutations. 

1.  The  formation  of  species  is  due  not  to  gradual 

changes,  but  to  sudden  mutations. 

2.  Natural  selection  presides  over  and  improves  varia- 

tions arising  from  mutation. 

From  extended  observations  on  the  variabihty  and  the 
adaptations  of  animals  and  plants,  from  the  results  of  experi- 
mental study  and  from  intensive  analysis  of  the  various  fac- 
tors proposed  to  explain  the  process  of  species-forming,  there 
has  resulted  a  remodeling  of  all  evolutionary  theories.  New 
theories  have  been  advanced  which,  in  their  relation  to  Dar- 
win's hypothesis  of  natural  selection,  fall  into  two  categories. 
There  are  competing  theories  designed  to  replace  that  of 
natural  selection;  and  there  are  auxihary,  or  supporting 
theories,  that  are  designed  to  throw  new  hght  on  the  condi- 
tions of  species-forming  and  to  strengthen  the  natural  selec- 
tion theory  by  its  more  complete  elucidation.  Such  an  ex- 
tensive literature  has  grown  up  in  the  discussion  of  these 
matters  that,  to  cover  it  with  any  show  of  adequacy,  re- 
quires separate  treatment,  with  specific  illustrations  and 
extended  comment.  The  entire  case  has  been  presented  with 
remarkable  clearness  in  Kellogg's  Darwinism  To-day,  and 
since  summaries  of  the  arguments  would  be  beyond  the 
purpose  of  this  book,  the  reader  is  referred  to  Kellogg's 
volume. 

There  are,  however,  two  ideas  of  such  fundamental  im- 
portance in  the  post-Darwinism  discussions  that  they  should 


THEORIES  OF  WEISMANN  AND  DE  VRIES  413 

receive  brief  consideration  here.  These  are  designated  re- 
spectively, orthogenesis  and  isolation.  Theodore  Eimer  is 
the  t}'pical  representative  of  the  ideas  of  orthogenesis.  He 
maintains  that  variations  of  organisms  take  place  not  for- 
tuitously in  radiating  and  heterogenous  Hnes,  but  follow  a 
few  definite  directions.  This  definitely  directed  evolution 
is  called  orthogenesis.  He  insists  that  there  is  continuous 
inheritance  of  acquired  characters,  and  he  is  radically  op- 
posed to  the  belief  that  natural  selection  plays  an  important 
part  in  evolution.  Variations  are  not  preserved  on  the  basis 
of  their  utility,  but  as  the  result  of  the  direct  inheritance  of 
acquired  characters.  His  theory  was  launched  in  1888  (Or- 
ganic Eovlution,  1889)  ^ii^j  ^s  developed  by  Eimer,  is  to  be 
classed  as  a  replacing  theory.  The  title  of  his  translated 
pamphlet,  published  in  English  in  1898,  On  Orthogenesis  and 
the  Impotence  of  Natural  Selection  in  Species-Formation,  is 
suggestive  as  to  his  position  in  reference  to  natural  selection. 
Isolation  as  a  favoring  (or  even  indispensable)  condition 
of  species-formation  has  been  championed  by  Moritz  Wagner 
(since  1868),  by  David  Starr  Jordan,  GuHck,  Romanes,  and 
others.  This  is  based  on  the  assumption  that  isolation  of 
species  has  played  an  essential  part  in  the  perpetuation  of 
variations.  Isolation  is  assumed  to  act  upon  variations  after 
they  are  started  and  not  to  play  an  important  part  in  pro- 
ducing variations.  The  basal  question  is,  Under  what  condi- 
tions will  variations  persist  and  become  intensified?  If  free 
intercrossings  occur,  it  seems  hkely  that  variations,  which 
at  the  beginning  are  slight,  will  tend  to  disappear.  Accord- 
ingly, it  will  be  advantageous  to  have  species  living  under 
such  conditions  of  segregation  that  those  possessing  similar 
variations  shall  be  compelled  to  breed  together.  This  would 
be  accomplished  by  isolation  of  species  either  by  geographical 
barriers  or  by  physiological  infertiHty  among  two  sections 
of  a  species  occupying  the  same  territory.    Romanes,  who  so 


414  BIOLOGY  AND  ITS  MAKERS 

to  speak,  was  Darwin's  personal  representative,  regarded 
isolation  as  an  indispensable  factor  to  the  strengthening  of 
variations  and  thus  bringing  about  the  changes  that  lead  to 
the  evolution  of  species. 

The  intensive  scrutiny  to  which  the  different  theories  of 
organic  evolution  have  been  subjected,  has  served  to  focahze 
attention  on  various  aspects  of  species  forming.  Natural 
selection  stands  forth  as  the  agency  to  direct  the  general 
course  of  evolution  after  it  is  started,  while  as  regards  the  be- 
ginnings, there  are  other  important  questions  as  the  causes 
of  variability,  that  await  further  investigation. 

The  cause  for  the  general  confusion  in  the  popular  mind 
regarding  any  distinction  between  organic  evolution  and 
Darwinism  is  not  far  to  seek.  As  has  been  shown,  Lamarck 
launched  the  doctrine  of  organic  evolution,  but  his  views  did 
not  even  get  a  public  hearing.  Then,  after  a  period  of  tem- 
porary disappearance,  the  doctrine  of  evolution  emerged 
again  in  1859.  And  this  time  the  discussion  of  the  general 
theory  centered  around  Darwin's  hypothesis  of  natural  selec- 
tion. It  is  quite  natural,  therefore,  that  people  should  think 
that  Darwinism  and  organic  evolution  are  synonymous  terms. 
The  distinction  between  the  general  theory  and  any  particular 
explanation  of  it  has,  I  trust,  been  made  sufficiently  clear  in 
the  preceding  pages. 


CHAPTER    XIX 

THE  RISE  OF  EVOLUTIONARY  THOUGHT 

A  CURRENT  of  evolutionary  thought  can  be  traced  through 
the  Uterature  dealmg  with  organic  nature  from  ancient  times. 
It  began  as  a  small  rill  among  the  Greek  philosophers  and 
dwindles  to  a  mere  thread  in  the  Middle  Ages,  sometimes 
almost  disappearing,  but  is  never  completely  broken  off. 
Near  the  close  of  the  eighteenth  century  it  suddenly  expands, 
and  becomes  a  broad  and  prevailing  influence  in  the  nine- 
teenth century.  Osborn,  in  his  book.  From  the  Greeks  to 
Darwin,  traces  the  continuity  of  evolutionary  thought  from 
the  time  of  the  Greek  philosophers  to  Darwin.  The  ancient 
phase,  although  interesting,  was  vague  and  general,  and 
may  be  dismissed  without  much  consideration.  After  the 
Renaissance  naturalists  were  occupied  with  other  aspects  of 
nature-study.  They  were  at  first  attempting  to  get  a  knowl- 
edge of  animals  and  plants  as  a  whole,  and  later  of  their 
structure,  their  developments,  and  their  physiology,  before 
questions  of  their  origin  were  brought  under  consideration. 

Opinion  before  Lamarck. — The  period  just  prior  to 
Lamarck  is  of  particular  interest.  Since  Lamarck  was  the 
first  to  give  a  comprehensive  and  consistent  theory  of  evolu- 
tion, it  will  be  interesting  to  determine  what  was  the  state 
of  opinion  just  prior  to  the  appearance  of  his  writings. 
Studies  of  nature  were  in  such  shape  at  that  time  that  the 
question  of  the  origin  of  species  arose,  and  thereafter  it  would 
not  recede.  This  was  owing  mainly  to  the  fact  that  Ray  and 
Linnaeus  by  defining  a  species  had  fixed  the  attention  of 

415 


4l6  BIOLOGY   AND    ITS    MAKERS 

naturalists  upon  the  distinguishing  features  of  the  particular 
kinds  of  animals  and  plants.  Are  species  realities  in  nature  ? 
The  consideration  of  this  apparently  simple  question  soon 
led  to  divergent  views,  and  then  to  warm  controversies  that 
extended  over  several  decades  of  time. 

The  view  first  adopted  without  much  thought  and  as  a 
matter  of  course  was  that  species  are  fixed  and  constant;  i.e., 
that  the  existing  forms  of  animals  and  plants  are  the  descend- 
ants of  entirely  similar  parents  that  were  originally  created 
in  pairs.  This  idea  of  the  fixity  of  species  was  elevated  to  the 
position  of  a  dogma  in  science  as  well  as  in  theology.  The 
opposing  view,  that  species  are  changeable,  arose  in  the 
minds  of  a  few  independent  observers  and  thinkers,  and,  as 
has  already  been  pointed  out,  the  discussion  of  this  question 
resulted  ultimately  in  a  complete  change  of  view  regarding 
nature  and  man's  relation  to  it.  When  the  conception  of 
evolution  came  upon  the  scene,  it  was  violently  combated. 
It  came  into  conflict  with  the  theory  designated  special 
creation. 

Views  of  Certain  Fathers  of  the  Church. — And  now  it  is 
essential  that  we  should  be  clear  as  to  the  sources  of  this 
dogma  of  special  creation.  It  is  perhaps  natural  to  assume 
that  there  was  a  conflict  existing  between  natural  science 
and  the  views  of  the  theologians  from  the  earliest  times; 
that  is,  between  the  scientific  method  and  the  method  of  the 
theologians,  the  latter  being  based  on  authority,  and  the 
former  upon  observation  and  experiment.  Although  there 
is  a  conflict  between  these  two  methods,  there  nevertheless 
was  a  long  period  in  which  many  of  the  leading  theological 
thinkers  were  in  harmony  with  the  men  of  science  with  refer- 
ence to  their  general  conclusions  regarding  creation.  Some 
of  the  early  Fathers  of  the  Church  exhibited  a  broader  and 
more  scientific  spirit  than  their  successors. 

St.  Augustine  (353-430),  in  the  fifth  century,  was  the 


RISE    OF    EVOLUTIONARY    THOUGHT  417 

first  of  the  great  theologians  to  discuss  specifically  the  ques- 
tion of  creation.  His  position  is  an  enlightened  one.  He 
says:  "It  very  often  happens  that  there  is  some  question  as 
to  the  earth  or  the  sky,  or  the  other  elements  of  this  world 
.  .  .  respecting  which  one  who  is  not  a  Christian  has  knowl- 
edge derived  from  most  certain  reasoning  or  observation" 
(that  is,  a  scientific  man) ;  "  and  it  is  very  disgraceful  and 
mischievous  and  of  all  things  to  be  carefully  avoided,  that  a 
Christian  speaking  of  such  matters  as  being  according  to  the 
Christian  Scriptures,  should  be  heard  by  an  unbeliever  talk- 
ing such  nonsense  that  the  unbeliever,  perceiving  him  to  be 
as  wide  from  the  mark  as  east  from  west,  can  hardly  restrain 
himself  from  laughing."     (Quoted  from  Osborn.) 

Augustine's  view  of  the  method  of  creation  was  that  of 
derivative  creation  or  creation  causaliter.  His  was  a  natural- 
istic interpretation  of  the  Mosaic  record,  and  a  theory  of 
gradual  creation.  He  held  that  in  the  beginning  the  earth 
and  the  waters  of  the  earth  were  endowed  with  power  to 
produce  plants  and  animals,  and  that  it  was  not  necessary  to 
assume  that  all  creation  was  formed  at  once.  He  cautions 
his  readers  against  looking  to  the  Scriptures  for  scientific 
truths.  He  said  in  reference  to  the  creation  that  the  days 
spoken  of  in  the  first  chapter  of  Genesis  could  not  be  solar 
days  of  twenty-four  hours  each,  but  that  they  must  stand 
for  longer  periods  of  time. 

.This  view  of  St.  Augustine  is  interesting  as  being  less 
narrow  and  dogmatic  than  the  position  assumed  by  many 
theologians  of  the  nineteenth  century. 

The  next  theologian  to  take  up  the  question  of  creation 
was  St.  Thomas  Aquinas  (12 25-1 274)  in  the  thirteenth  cen- 
tury. He  quotes  St.  Augustine's  view  with  approval,  but 
does  not  contribute  anything  of  his  own.  One  should  not 
hastily  conclude,  however,  because  these  views  were  held  by 
leaders  of  theological  thought,  that  they  were  universally 


4i8  BIOLOGY   AND    ITS    MAKERS 

accepted.  *'The  truth  is  that  all  classes  of  theologians 
departed  from  the  original  philosophical  and  scientific  stand- 
ards of  some  of  the  Fathers  of  the  Church,  and  that  special 
creation  became  the  universal  teaching  from  the  middle  of 
the  sixteenth  to  the  middle  of  the  nineteenth  centuries." 

The  Doctrine  of  Special  Creation. — About  the  seven- 
teenth century  a  change  came  about  w^hich  v^as  largely  owing 
to  the  writings  and  influence  of  a  Spanish  theologian  named 
Suarez  (1548-1617).  Although  Suarez  is  not  the  sole 
founder  of  this  conception,  it  is  certain,  as  Huxley  has  shown, 
that  he  engaged  himself  with  the  questions  raised  by  the  Bib- 
lical account  of  creation;  and,  furthermore,  that  he  opposed 
the  views  that  had  been  expressed  by  Augustine.  In  his 
tract  upon  the  work  of  the  six  days  {Tractatus  de  opere  sex 
dierum)  he  takes  exception  to  the  views  expressed  by  St. 
Augustine;  he  insisted  that  in  the  Scriptural  account  of 
creation  a  day  of  twenty-four  hours  was  meant,  and  in  all 
other  cases  he  insists  upon  a  literal  interpretation  of  the 
Scriptures.  Thus  he  introduced  into  theological  thought  the 
doctrine  which  goes  under  the  name  of  special  creation. 
The  interesting  feature  in  all  this  is  that  from  the  time  of 
St.  Augustine,  in  the  fifth  century,  to  the  time  when  the  ideas 
of  Suarez  began  to  prevail,  in  the  seventeenth,  there  had  been 
a  harmonious  relation  between  some  of  the  leading  theolo- 
gians and  scientific  men  in  their  outlook  upon  creation. 

The  opinion  of  Augustine  and  other  theologians  was 
largely  owing  to  the  influence  of  Aristotle.  *'We  know," 
says  Osborn,  "  that  Greek  philosophy  tinctured  early  Chris- 
tian theology;  what  is  not  so  generally  realized  is  that  the 
Aristotelian  notion  of  the  development  of  life  led  to  the  true 
interpretation  of  the  Mosaic  account  of  the  creation. 

"There  was  in  fact  a  long  Greek  period  in  the  history 
of  the  evolutionary  idea  extending  among  the  Fathers  of  the 
Church  and  later  among  some  of  the  schoolmen,   in  their 


RISE    OF    EVOLUTIONARY   THOUGHT  419 

commentaries  upon  creation,  which  accord  very  closely  with 
the  modern  theistic  conception  of  evolution.  If  the  ortho- 
doxy of  Augustine  had  remained  the  teaching  of  the  Church, 
the  final  establishment  of  evolution  would  have  come  far 
earlier  than  it  did,  certainly  during  the  eighteenth  century 
instead  of  the  nineteenth  century,  and  the  bitter  controversy 
over  this  truth  of  nature  would  never  have  arisen." 

The  conception  of  special  creation  brought  into  especial 
prominence  upon  the  Continent  by  Suarez  was  taken  up  by 
John  Milton  in  his  great  epic  Paradise  Lost,  in  which  he 
gave  a  picture  of  creation  that  molded  into  specific  form 
the  opinion  of  the  English-speaking  clergy  and  of  the 
masses  who  read  his  book.  When  the  doctrine  of  organic 
evolution  was  announced,  it  came  into  conflict  with  this 
particular  idea;  and,  as  Huxley  has  very  pointedly  remarked, 
the  new  theory  of  organic  evolution  found  itself  in  conflict 
with  the  Miltonic,  rather  than  the  Mosaic  cosmology.  All  this 
represents  an  interesting  phase  in  intellectual  development. 

Forerunners  of  Lamarck. — We  now  take  up  the  imme- 
diate predecessors  of  Lamarck.  Those  to  be  mentioned  are 
Buff  on,  Erasmus  Darwin,  and  Goethe. 

Buffon  (1707-1788)  (Fig.  116),  although  of  a  more  philo- 
sophical mind  than  many  of  his  contemporaries,  was  not  a 
true  investigator.  That  is,  he  left  no  technical  papers  or 
contributions  to  science.  From  1739  to  the  time  of  his  death 
he  was  the  superintendent  of  the  Jardin  du  Rot.  He  was  a 
man  of  elegance,  with  an  assured  position  in  society.  He 
was  a  delightful  writer,  a  circumstance  that  enabled  him  to 
make  natural  history  popular.  It  is  said  that  the  advance 
sheets  of  Buffon's  Histoire  Naturelle  were  to  be  found  on  the 
tables  of  the  boudoirs  of  ladies  of  fashion.  In  that  work  he 
suggested  the  idea  that  the  different  forms  of  life  were  grad- 
ually produced,  but  his  timidity  and  his  prudence  led  him 
to  be  obscure  in  what  he  said. 


420  BIOLOGY   AND    ITS    MAKERS 

Packard,  who  has  studied  his  writings  with  care,  says 
that  he  was  an  evolutionist  through  all  periods  of  his  life,  not, 
as  is  commonly  maintained,  believing  first  in  the  fixity  of 
species,  later  in  their  changeability,  and  lastly  returning  to 
his  earUer  position.     ''The  impression  left  on  the  mind  after 


Fig.   ii6. — Buffon,   1707-1788. 

reading  Buffon  is  that  even  if  he  threw  out  these  suggestions 
and  then  retracted  them,  from  fear  of  annoyance  or  even 
persecution  from  the  bigots  of  his  time,  he  did  not  himself 
always  take  them  seriously,  but  rather  jotted  them  down  as 
passing  thoughts.     Certainly  he  did  not  present  them  in  the 


RISE    OF    EVOLUTIONARY   THOUGHT  421 

formal,  forcible,  and  scientific  way  that  Erasmus  Darwin  did. 
The  result  is  that  the  tentative  views  of  Buffon,  which  have 
to  be  with  much  research  extracted  from  the  forty-four  vol- 
umes of  his  works,  would  now  be  regarded  as  in  a  degree 
superficial  and  valueless.  But  they  appeared  thirty-four 
years  before  Lamarck's  theory,  and  though  not  epoch-making, 


Fig.   117. — Erasmus  Darwin,   1731-1802. 

they  are  such  as  will  render  the  name  of  Buffon  memorable 
for  all  time."     (Packard.) 

Erasmus  Darwin  (Fig.  117)  was  the  greatest  of  Lamarck's 
predecessors.  In  1794  he  pubhshed  the  Zoonomia.  In  this 
work  he  stated  ten  principles;  among  them  he  vaguely 
suggested  the  transmission  of  acquired  characteristics,  the 
law  of  sexual  selection — or  the  law  of  battle,  as  he  called  it — 


422  BIOLOGY    AND    ITS    MAKERS 

protective  coloration,  etc.  His  work  received  some  notice 
from  scholars.  Paley's  Natural  Theology,  for  illustration, 
was  written  against  it,  although  Paley  is  careful  not  to  men- 
tion Darwin  or  his  work.  The  success  of  Paley's  book  is 
probably  one  of  the  chief  causes  for  the  neglect  into  which 
the  views  of  Buff  on  and  Erasmus  Darwin  fell. 

Inasmuch  as  Darwin's  conclusions  were  published  before 
Lamarck's  book,  it  would  be  interesting  to  determine  whether 
or  not  Lamarck  was  influenced  by  him.  The  careful  con- 
sideration of  this  matter  leads  to  the  conclusion  that  Lamarck 
drew  his  inspiration  directly  from  nature,  and  that  points  of 
similarity  between  his  views  and  those  of  Erasmus  Darwin 
are  to  be  looked  upon  as  an  example  of  paralleUsm  in 
thought.  It  is  altogether  likely  that  Lamarck  was  wholly  un- 
acquainted with  Darwin's  work,  which  had  been  published 
in  England. 

Goethe's  connection  with  the  rise  of  evolutionary  thought 
is  in  a  measure  incidental.  In  1790  he  published  his  Meta- 
morphosis of  Plants,  showing  that  flowers  are  modified 
leaves.  This  doctrine  of  metamorphosis  of  parts  he  presently 
applied  to  the  animal  kingdom,  and  brought  forward 
his  famous,  but  erroneous,  vertebrate  theory  of  the  skull. 
As  he  meditated  on  the  extent  of  modifications  there  arose 
in  his  mind  the  conviction  that  all  plants  and  animals  have 
been  evolved  from  the  modification  of  a  few  parental  types. 
Accordingly  he  should  be  accorded  a  place  in  the  history  of 
evolutionary  thought. 

Opposition  to  Lamarck's  Views. — Lamarck's  doctrine, 
which  was  published  in  definite  form  in  1809,  has  been 
already  outlined.  We  may  well  inquire,  Why  did  not  his 
views  take  hold  ?  In  the  first  place,  they  were  not  accepted 
by  Cuvier.  Cuvier's  opposition  was  strong  and  vigorous, 
and  succeeded  in  causing  the  theory  of  Lamarck  to  be  com- 
pletely neglected  by  the  French  people.     Again,  we  must 


RISE    OF    EVOLUTIONARY    THOUGHT  423 

recognize  that  the  time  was  not  ripe  for  the  acceptance  of 
such  truths;  and,  finally,  that  there  was  no  great  principle 
enunciated  by  Lamarck  which  could  be  readily  understood 
as  there  was  in  Darwin's  book  on  the  doctrine  of  natural 
selection. 

The  temporary  disappearance  of  the  doctrine  of  organic 
evolution  which  occurred  after  Lamarck  expounded  his  theory 
was  also  owing  to  the  reaction  against  the  speculations  of 
the  school  of  Natur-Philosophie.  The  extravagant  specula- 
tion of  Oken  and  the  other  representatives  of  this  school 
completely  disgusted  men  who  were  engaged  in  research  by 
observation  and  experiment.  The  reaction  against  that 
school  was  so  strong  that  it  was  difficult  to  get  a  hearing  for 
any  theoretical  speculation;  but  Cuvier's  influence  must  be 
looked  upon  as  the  chief  one  in  causing  disregard  for  La- 
marck's writings. 

The  work  of  Cuvier  has  been  already  considered  in  con- 
nection both  with  comparative  anatomy  and  zoology,  but 
a  few  points  must  still  be  held  under  consideration.  Cuvier 
brought  forward  the  idea  of  catastrophism  in  order  to  explain 
the  disappearance  of  the  groups  of  fossil  animals.  He  be- 
lieved in  the  doctrine  of  spontaneous  generation.  He  held 
to  the  doctrine  of  pre-delineation,  so  that  it  must  be  admitted 
that  whenever  he  forsook  observation  for  speculation  he 
was  singularly  unhappy ,  and  it  is  undeniable  that  his  posi- 
tion of  hostility  in  reference  to  the  speculation  of  Lamarck 
retarded  the  progress  of  science  for  nearly  half  a  century. 

Cuvier  and  Saint-Hilaire.— In  1830  there  occurred  a 
memorable  controversy  between  Cuvier  and  Saint-Hilaire. 
The  latter  (Fig.  118)  was  in  early  life  closely  associated  with 
Lamarck,  and  shared  his  views  in  reference  to  the  origin  of 
animals  and  plants;  though  in  certain  points  Saint-Hilaire 
was  more  a  follower  of  Buff  on  than  of  Lamarck.  Strangely 
enough,  Saint-Hilaire  was  regarded  as  the  stronger  man  of 


424 


BIOLOGY   AND    ITS    MAKERS 


the  two.  He  was  more  in  the  pubUc  eye,  but  was  not  a  man 
of  such  deep  intellectuaUty  as  Lamarck.  His  scientific  repu- 
tation rests  mainly  upon  his  Philosophie  Anatomique.  The 
controversy  between  him  and  Cuvier  was  on  the  subject  of 


Fig.   ii8. — Geoffroy  Saint-Hilaire,   1772-1844. 


unity  of  type;  but  it  involved  the  question  of  the  fixity  or 
mutability  of  species,  and  therefore  it  involved  the  foundation 
of  the  question  of  organic  evolution. 

This  debate  stirred  all  intellectual  Europe.     Cuvier  won 
as  being  the  better  debater  and  the  better   manager  of  his 


I 


RISE    OF    EVOLUTIONARY   THOUGHT  425 

case.  He  pointed  triumphantly  to  the  four  branches  of  the 
animal  kingdom  which  he  had  established,  maintaining  that 
these  four  branches  represented  four  distinct  types  of  organi- 
zation ;  and,  furthermore,  that  fixity  of  species  and  fixity  of 
type  were  necessary  for  the  existence  of  a  scientific  natural 
history.  We  can  see  now  that  his  contention  was  wrong, 
but  at  the  time  he  won  the  debate.  The  young  men  of 
the  period,  that  is,  the  rising  biologists  of  France,  were 
nearly  all  adherents  of  Cuvier,  so  that  the  effect  of  the  de- 
bate was,  as  previously  stated,  to  retard  the  progress  of  sci- 
ence. This  noteworthy  debate  occurred  in  February,  1830. 
The  wide  and  lively  interest  with  which  the  debate  was 
followed  may  be  inferred  from  the  excitement  manifested 
by  Goethe.  Of  the  great  poet-naturalist,  who  was  then  in 
his  eighty-first  year,  the  following  incident  is  told  by  Soret : 

"Monday,  Aug.  2d,  1830. — ^The  news  of  the  outbreak  of 
the  revolution  of  July  arrived  in  Weimar  to-day,  and  has 
caused  general  excitement.  In  the  course  of  the  afternoon 
I  went  to  Goethe.  '  Well,'  he  exclaimed  as  I  entered,  *  what 
do  you  think  of  this  great  event  ?  The  volcano  has  burst 
forth,  all  is  in  flames,  and  there  are  no  more  negotiations 
behind  closed  doors.'  *A  dreadful  affair,'  I  answered; 
*but  what  else  could  be  expected  under  the  circumstances, 
and  with  such  a  ministry,  except  that  it  would  end  in  the 
expulsion  of  the  present  royal  family?'  *We  do  not  seem 
to  understand  each  other,  my  dear  friend,'  replied  Goethe. 
*I  am  not  speaking  of  those  people  at  all;  I  am  interested 
in  something  very  different.  I  mean  the  dispute  between 
Cuvier  and  Geoffroy  de  Saint-Hilaire,  which  has  broken  out 
in  the  Academy,  and  which  is  of  such  great  importance  to 
science.'  This  remark  of  Goethe  came  upon  me  so  unex- 
pectedly that  I  did  not  know  what  to  say,  and  my  thoughts 
for  some  minutes  seemed  to  have  come  to  a- complete  stand- 
still.    *The  affair  is  of  the  utmost  importance,'   he  con- 


426  BIOLOGY   AND    ITS    MAKERS 

tinued,  'and  you  can  not  form  any  idea  of  what  I  felt  on 
receiving  the  news  of  the  meeting  on  the  19th.  In  Geoffroy 
de  Saint-Hilaire  we  have  now  a  mighty  ally  for  a  long  time 
to  come.  But  I  see  also  how  great  the  sympathy  of  the 
French  scientific  world  must  be  in  this  affair,  for,  in  spite  of 
the  terrible  political  excitement,  the  meeting  on  the  19th 
was  attended  by  a  full  house.  The  best  of  it  is,  however, 
that  the  synthetic  treatment  of  nature,  introduced  into 
France  by  Geoffroy,  can  now  no  longer  be  stopped.  This 
matter  has  now  become  public  through  the  discussions  in  the 
Academy,  carried  on  in  the  presence  of  a  large  audience; 
it  can  no  longer  be  referred  to  secret  committees,  or  be  settled 
or  suppressed  behind  closed  doors.'  " 

Influence  of  LyelPs  Principles  of  Geology. — But  just  as 
Cuvier  was  triumphing  over  Saint-Hilaire  a  work  was  being 
published  in  England  which  was  destined  to  overthrow  the 
position  of  Cuvier  and  to  bring  again  a  sufficient  foundation 
for  the  basis  of  mutability  of  species.  I  refer  to  Lycll's 
Principles  of  Geology,  the  influence  of  which  has  already 
been  spoken  of  in  Chapter  XV.  Lyell  laid  down  the  prin- 
ciple that  we  are  to  interpret  occurrences  in  the  past  in  the 
terms  of  what  is  occurring  in  the  present.  He  demonstrated 
that  observations  upon  the  present  show  that  the  surface  of 
the  earth  is  undergoing  gradually  slow  changes  through  the 
action  of  various  agents,  and  he  pointed  out  that  we  must 
view  the  occurrences  in  the  past  in  the  light  of  occurrences 
in  the  present.  Once  this  was  applied  to  animal  forms  it 
became  evident  that  the  observations  upon  animals  and  plants 
in  the  present  must  be  applied  to  the  life  of  the  fossil  series. 

These  ideas,  then,  paved  the  way  for  the  conception  of 
changes  in  nature  as  being  one  continuous  series. 

H.  Spencer. — In  1852  came  the  publication  of  Herbert 
Spencer  in  the  Leader,  in  which  he  came  very  near  antici- 
pating  the  doctrine  of  natural  selection.     He  advanced  the 


RISE    OF    EVOLUTIONARY   THOUGHT  427 

developmental  hypothesis,  saying  that  even  if  its  supporters 
could  ^'merely  show  that  the  production  of  species  by  the 
process  of  modification  is  conceivable,  they  would  be  in  a 
better  position  than  their  opponents.  But  they  can  do  much 
more  than  this ;  they  can  show  that  the  process  of  modifica- 
tion has  affected  and  is  affecting  great  changes  in  all  organ- 
isms subject  to  modifying  influences.  .  .  .  They  can  show 
that  any  existing  species,  animal  or  vegetable,  when  placed 
under  conditions  different  from  its  previous  ones,  imme- 
diately begins  to  undergo  certain  changes  of  structure  fitting 
it  for  the  new  conditions.  They  can  show  that  in  successive 
generations  these  changes  continue,  until  ultimately  the 
new  conditions  become  the  natural  ones.  They  can  show 
that  in  cultivated  plants  and  domesticated  animals,  and  in  the 
several  races  of  men,  these  changes  have  uniformly  taken 
place.  They  can  show  that  the  degrees  of  difference  so  pro- 
duced are  often,  as  in  dogs,  greater  than  those  on  which  dis- 
tinctions of  species  are  in  other  cases  founded.  They  can  show 
that  it  is  a  matter  of  dispute  whether  some  of  these  modified 
forms  are  varieties  or  modified  species.  And  thus  they  can 
show  that  throughout  all  organic  nature  there  is  at  work  a 
modifying  influence  of  the  kind  they  assign  as  the  cause  of 
these  specific  differences;  an  influence  which,  though  slow 
in  its  action,  does  in  time,  if  the  circumstances  demand  it, 
produce  marked  changes;  an  influence  which,  to  all  appear- 
ance, would  produce  in  the  millions  of  years,  and  under  the 
great  varieties  of  conditions  which  geological  records  imply, 
any  amount  of  change." 

"It  is  impossible,"  says  Marshall,  "to  depict  better  than 
this  the  condition  prior  to  Darwin.  In  this  essay  there  is  full 
recognition  of  the  fact  of  transition,  and  of  its  being  due  to 
natural  influences  or  causes,  acting  now  and  at  all  times. 
Yet  it  remained  comparatively  unnoticed,  because  Spencer, 
like  his  contemporaries  and  predecessors,  while  advocating 


428  BIOLOGY   AND    ITS    MAKERS 

evolution,  was  unable  to  state  explicitly  what  these  causes 
were." 

Darwin  and  Wallace. — In  1858  we  come  to  the  crown- 
ing event  in  the  rise  of  evolutionary  thought,  when  Alfred 
Russel  Wallace  sent  a  communication  to  Mr.  Darwin,  beg- 
ging him  to  look  it  over  and  give  him  his  opinion  of  it.  Darwin, 
who  had  been  working  upon  his  theory  for  more  than  twenty 
years,  patiently  gathering  facts  and  testing  the  same  by 
experiment,  was  greatly  surprised  to  find  that  Mr.  Wallace 
had  independently  hit  upon  the  same  principle  of  explaining 
the  formation  of  species.  In  his  generosity,  he  was  at  first 
disposed  to  withdraw  from  the  field  and  publish  the  essay  of 
Wallace  without  saying  anything  about  his  own  work.  He 
decided,  however,  to  abide  by  the  decision  of  two  of  his 
friends,  to  whom  he  had  submitted  the  matter,  and  the  result 
was  that  the  paper  of  Wallace,  accompanied  by  earlier  com- 
munications of  Darwin,  were  laid  before  the  Linnaean  Society 
of  London.  This  was  such  an  important  event  in  the  his- 
tory of  science  that  its  consideration  is  extended  by  quoting 
the  following  letter: 

"London,  June  30th,  1858. 

"My  Dear  Sir:  The  accompanying  papers,  which  we 
have  the  honor  of  communicating  to  the  Linnaean  Society, 
and  which  all  relate  to  the  same  subject;  viz.,  the  laws  which 
affect  the  production  of  varieties,  races,  and  species,  contain 
the  results  of  the  investigations  of  two  indefatigable  natural- 
ists, Mr.  Charles  Darwin  and  Mr.  Alfred  Wallace. 

"These  gentlemen  having,  independently  and  unknown 
to  one  another,  conceived  the  same  very  ingenious  theory  to 
account  for  the  appearance  and  perpetuation  of  varieties 
and  of  specific  forms  on  our  planet,  may  both  fairly  claim  the 
merit  of  being  original  thinkers  in  this  important  line  of 
inquiry;    but  neither  of  them  having  published  his  views. 


I 


RISE    OF    EVOLUTIONARY    THOUGHT  429 

though  Mr.  Darwin  has  for  many  years  past  been  repeatedly 
urged  by  us  to  do  so,  and  both  authors  having  now  unreserv- 
edly placed  their  papers  in  our  hands,  we  think  it  would 
best  promote  the  interests  of  science  that  a  selection  from 
them  should  be  laid  before  the  Linnaean  Society. 

"Taken  in  the  order  of  their  dates,  they  consist  of: 

"  I.  Extracts  from  a  MS.  work  on  species,  by  Mr.  Dar- 
win, which  was  sketched  in  1839  and  copied  in  1844,  when 
the  copy  was  read  by  Dr.  Hooker,  and  its  contents  afterward 
communicated  to  Sir  Charles  Lyell.  The  first  part  is  devoted 
to  The  Variation  of  Organic  Beings  under  DomesticaHon  and 
in  their  Natural  State;  and  the  second  chapter  of  that  part, 
from  which  we  propose  to  read  to  the  Society  the  extracts 
referred  to,  is  headed  On  the  Variation  of  Organic  Beings  in 
a  State  of  Nature ;  on  the  Natural  Means  of  Selection;  on  the 
Comparison  of  Domestic  Races  and  True  Species. 

"2.  An  abstract  of  a  private  letter  addressed  to  Professor 
Asa  Gray,  of  Boston,  U.  S.,  in  October,  1857,  by  Mr.  Darwin, 
in  which  he  repeats  his  views,  and  which  shows  that  these 
remained  unaltered  from  1839  to  1857. 

"3.  An  essay  by  Mr.  Wallace,  entitled  On  the  Tendency 
of  Varieties  to  Depart  Indefinitely  from  the  Original  Type, 
This  was  written  at  Ternate  in  February,  1858,  for  the 
perusal  of  his  friend  and  correspondent,  Mr.  Darwin,  and 
sent  to  him  with  the  expressed  wish  that  it  should  be  for- 
warded to  Sir  Charles  Lyell,  if  Mr.  Darwin  thought  it  suffi- 
ciently novel  and  interesting.  So  highly  did  Mr.  Darwin 
appreciate  the  value  of  the  views  therein  set  forth  that  he 
proposed,  in  a  letter  to  Sir  Charles  Lyell,  to  obtain  Mr. 
Wallace's  consent  to  allow  the  essay  to  be  pubHshed  as  soon 
as  possible.  Of  this  step  we  highly  approved,  provided  Mr. 
Darwin  did  not  withhold  from  the  public,  as  he  was  strongly 
inclined  to  do  (in  favor  of  Mr.  Wallace),  the  memoir  which 
he  had  himself  written  on  the  same  subject,  and  which,  as 


I 


430  BIOLOGY   AND    ITS    MAKERS 

before  stated,  one  of  us  had  perused  in  1844,  and  the  con- 
tents of  which  we  had  both  of  us  been  privy  to  for  many  years. 

'^  On  representing  this  to  Mr.  Darwin,  he  gave  us  permis- 
sion to  make  what  use  we  thought  proper  of  his  memoir,  etc. ; 
and  in  adopting  our  present  course,  of  presenting  it  to  the 
Linnaean  Society,  we  have  explained  to  him  that  we  are  not 
solely  considering  the  relative  claims  to  priority  of  himself 
and  his  friend,  but  the  interests  of  science  generally;  for  we 
feel  it  to  be  desirable  that  views  founded  on  a  wide  deduction 
from  facts,  and  matured  by  years  of  reflecting,  should  con- 
stitute at  once  a  goal  from  which  others  may  start ;  and  that, 
while  the  scientific  world  is  waiting  for  the  appearance  of 
Mr.  Darwin's  complete  work,  some  of  the  leading  results  of 
his  labours,  as  well  as  those  of  his  able  correspondent,  should 
together  be  laid  before  the  pubHc. 

''We  have  the  honour  to  be  yours  very  obediently, 

Charles  Lyell, 
Jos.  D.  Hooker." 

Personality  of  Darwin. — The  personality  of  Darwin  is 
extremely  interesting.  Of  his  numerous  portraits,  the  one 
shovel  in  Fig.  119  is  less  commonly  known  than  those  show- 
ing him  with  a  beard  and  a  much  furrowed  forehead.  This 
portrait  represents  him  in  middle  life,  about  the  time  of  the 
publication  of  his  Origin  of  Species.  It  shows  a  rather 
typical  British  face,  of  marked  individuality.  Steadiness, 
sincerity,  and  urbanity  are  all  depicted  here.  His  bluish- 
gray  eyes  were  overshadowed  by  a  projecting  ridge  and  very 
prominent,  bushy  eyebrows  that  make  his  portrait,  once  seen, 
easily  recognized  thereafter.  In  the  full-length  portraits 
representing  him  seated,  every  line  in  his  body  shows  the  quiet, 
philosophical  temper  for  which  he  was  notable.  An  intimate 
account  of  his  life  is  contained  in  the  Life  and  Letters  0) 
Charles  Darwin  (1887)  and  in  More  Letters  oj  Darwin^igoT,), 


RISE    OF    EVOLUTIONARY   THOUGHT  431 

both  of  which  are  illustrated  by  portraits  and  other  pictures. 
The  books  about  Darwin  and  his  work  are  numerous,  but 
the  reader  is  referred  in  particular  to  the  two  mentioned  as 
giving  the  best  conception  of  the  great  naturalist  and  of  his 
personal  characteristics. 

He  is  described  as  being  about  six  feet  high,  but  with  a 
stoop  of  the  shoulders  which  diminished  his  apparent  height; 


Fig.   119. — Charles  Darwin,   1809-1882, 

"of  active  habits,  but  with  no  natural  grace  or  neatness  of 
movement."  *'In  manner  he  was  bright,  animated,  and 
cheerful;  a  delightfully  considerate  host,  a  man  of  never- 
failing  courtesy,  leading  him  to  reply  at  length  to  letters 
from  anybody,  and  sometimes  of  a  most  foolish  kind.'^ 

His  Home  Life. — "  Darwin  was  a  man  greatly  loved  and 
respected  by  all  who  knew  him.     There  was  a  peculiar  charm 


432  BIOLOGY   AND    ITS    MAKERS 

about  his  manner,  a  constant  deference  to  others,  and  a 
faculty  for  seeing  the  best  side  of  everything  and  every- 
body." 

He  was  most  affectionate  and  considerate  at  home.  The 
picture  of  Darwin's  hfe  with  his  children  gives  a  glimpse 
of  the  tenderness  and  deep  affection  of  his  nature,  and  the 
reverent  regard  with  which  he  was  held  in  the  family  circle 
is  very  touching.  One  of  his  daughters  writes:  ''My  first 
remembrances  of  my  father  are  of  the  delights  of  his  playing 
with  us.  He  was  passionately  attached  to  his  own  children, 
although  he  was  not  an  indiscriminate  child-lover.  To  all 
of  us  he  was  the  most  delightful  playfellow,  and  the  most 
perfect  sympathizer.  Indeed,  it  is  impossible  adequately  to 
describe  how  delightful  a  relation  his  was  to  his  family, 
whether  as  children  or  in  their  later  life. 

"It  is  a  proof  of  the  terms  on  which  we  were,  and  also  of 
how  much  he  was  valued  as  a  playfellow,  that  one  of  his  sons, 
when  about  four  years  old,  tried  to  bribe  him  with  a  sixpence 
to  come  and  play  in  working  hours.  We  all  knew  the  sacred- 
ness  of  working  time,  but  that  any  one  should  resist  sixpence 
seemed  an  impossibility." 

Method  of  Work. — Darwin's  Ufe,  as  might  be  inferred 
from  the  enduring  quality  of  his  researches,  shows  an 
unswerving  purpose.  His  theory  was  not  the  result  of  a 
sudden  flash  of  insight,  nor  was  it  struck  out  in  the  heat 
of  inspiration,  but  was  the  product  of  almost  unexampled 
industry  and  conscientious  endeavor  in  the  face  of  unfavor- 
able circumstances.  Although  strikingly  original  and  inde- 
pendent as  a  thinker,  he  was  slow  to  arrive  at  conclusions, 
examining  with  the  most  minute  and  scrupulous  care  the 
ground  for  every  conclusion.  "One  quality  of  mind  that 
seemed  to  be  of  especial  advantage  in  leading  him  to  make 
discoveries  was  the  habit  of  never  letting  exceptions  pass 
unnoticed."     He  enjoyed  experimenting  much  more  than 


RISE    OF    EVOLUTIONARY    THOUGHT  433 

work  which  only  entailed  reasoning.  Of  course,  he  was  a 
great  reader,  but  for  books  as  books  he  had  no  respect,  often 
cutting  large  ones  in  two  in  order  to  make  them  easier  to 
hold  while  in  use. 

Darwin^s  Early  Life. — Charles  Darwin  was  born  in  1809 
at  Shrewsbury,  England,  of  distinguished  ancestry,  his  grand- 
father being  the  famous  Dr.  Erasmus  Darwin,  the  founder, 
as  we  have  seen,  of  a  theory  of  evolution.  In  his  youth  he 
gave  no  indication  of  future  greatness.  He  was  sent  to 
Edinburgh  to  study  medicine,  but  that  the  work  |ailed  to 
arouse  in  him  an  absorbing  interest  is  shown  by  his  charac- 
terizing some  of  the  lectures  as  "  incredibly  dull."  After  two 
sessions,  at  the  suggestion  of  his  father,  he  left  Edinburgh  to 
study  for  the  Church.  He  then  entered  Christ's  College, 
Cambridge,  where  he  remained  for  three  years.  After  ta- 
king his  baccalaureate  degree  at  Cambridge,  where  he  had 
manifested  an  interest  in  scientific  study,  and  had  been 
encouraged  by  Professor  Henslow,  came  the  event  which 
proved,  as  Darwin  says,  ''the  turning-point  of  my  life." 
This  was  his  appointment  as  naturalist  on  the  surveying 
expedition  about  to  be  entered  upon  by  the  ship  Beagle. 
An  amusing  circumstance  connected  with  his  appointment 
is  that  he  was  nearly  rejected  by  Captain  Fitz-Roy,  who 
doubted  "whether  a  man  with  such  a  shaped  nose  could 
possess  sufficient  energy  and  determination  for  the  voyage." 

Voyage  of  the  Beagle. — The  voyage  of  the  Beagle  ex- 
tended over  five  years  (1831-1836),  mainly  along  the  west 
coast  of  South  America.  It  was  on  this- voyage  that  Darwin 
acquired  the  habit  of  constant  industry.  He  had  also  oppor- 
tunity to  take  long  trips  on  shore,  engaged  in  observation 
and  in  making  extensive  collections.  He  observed  nature  in 
the  field  under  exceptional  circumstances.  As  he  traveled 
he  noted  fossil  forms  in  rocks  as  well  as  the  living  forms  in 
field  and  forest.     He  observed  the  correspondence  in  type 


> 


434  BIOLOGY   AND    ITS    MAKERS 

between  certain  extinct  forms  and  recent  animals  in  South 
America.  He  noticed  in  the  Galapagos  Islands  a  fauna  similar 
in  general  characteristics  to  that  of  the  mainland,  five  or  six 
hundred  miles  distant,  and  yet  totally  different  as  to  species. 
Moreover,  certain  species  were  found  to  be  confined  to  par- 
ticular islands.  These  observations  awakened  in  his  mind, 
a  mind  naturally  given  to  inquiring  into  the  causes  of  things, 
questions  that  led  to  the  formulation  of  his  theory.  It  was 
not,  however,  until  1837  that  he  commenced  his  first  note- 
book for  containing  his  observations  upon  the  transmutations 
of  animals.  He  started  as  a  firm  believer  in  the  fixity  of 
species,  and  spent  several  years  collecting  and  considering 
data  before  he  changed  his  views. 

At  Down. — On  his  return  to  England,  after  spending 
some  time  in  London,  he  purchased  a  country-place  at  Down 
and,  as  his  inheritance  made  it  possible,  he  devoted  himself 
entirely  to  his  researches. 

But,  as  is  well  known,  he  found  in  his  illness  a  great 
obstacle  to  steady  work.  He  had  been  a  vigorous  youth  and 
young  man,  fond  of  outdoor  sports,  as  fishing,  shooting, 
and  the  like.  After  returning  from  his  long  voyage,  he  was 
affected  by  a  form  of  constant  illness,  involving  a  giddiness 
in  the  head,  and  "for  nearly  forty  years  he  never  knew  one 
day  of  the  health  of  an  ordinary  man,  and  thus  his  life  was 
one  long  struggle  against  the  weariness  and  strain  of  sick- 
ness." Gould  in  his  Biographical  Clinics  attributes  his  ill- 
ness to  eye- strain. 

"  Under  such  conditions  absolute  regularity  of  routine  was 
essential,  and  the  day's  work  was  carefully  planned  out.  At 
his  best,  he  had  three  periods  of  work:  from  8.00  to  9.30; 
from  10.30  to  12.15;  ^^^  irova  4.30  to  6.00,  each  period  being 
under  two  hours'  duration." 

The  patient  thoroughness  of  his  experimental  work  and  of 
his  observation  is  shown  by  the  fact  that  he  did  not  publish 


RISE    OF    EVOLUTIONARY   THOUGHT  435 

his  book  on  the  Origin  oj  Species  until  he  had  worked  on 
his  theory  twenty-two  years.  The  circumstances  that  led 
to  his  publishing  it  when  he  did  have  already  been  indi- 
cated. 

Parallelism  in  the  Thought  of  Darwin  and  Wallace. — 
No  one  can  read  the  letters  of  Darwin  and  Wallace  explaining 
how  they  arrived  at  their  idea  of  natural  selection  without 
marveling  at  the  remarkable  parallelism  in  the  thought  of  the 
two.  It  is  a  noteworthy  circumstance  that  the  idea  of  natural 
selection  came  to  both  by  the  reading  of  the  same  book,  Mal- 
ihus  on  Population, 

Darwin's  statement  of  how  he  arrived  at  the  concep- 
tion of  natural  selection  is  as  follows:  "In  October,  1838, 
that  is,  fifteen  months  after  I  had  begun  my  systematic 
inquiry,  I  happened  to  read  for  amusement  Malthus  on 
Population,  and  being  well  prepared  to  appreciate  the 
struggle  for  existence  which  everywhere  goes  on  from  long- 
continued  observations  of  the  habits  of  animals  and  plants, 
it  at  once  struck  me  that  under  these  circumstances  favourable 
variations  would  tend  to  be  preserved  and  unfavourable  ones 
to  be  destroyed.  The  result  oj  this  would  he  the  formation 
of  new  species.  Here  then  I  had  at  last  got  a  theory  by 
which  to  work,  but  I  was  so  anxious  to  avoid  prejudice  that 
I  determined  not  for  some  time  to  write  even  the  briefest 
sketch  of  it.  In  June,  1842,  I  first  allowed  myself  the  satis- 
faction of  writing  a  very  brief  abstract  of  my  theory  in  pencil, 
in  thirty-five  pages,  and  this  was  enlarged  during  the  summer 
of  1844  into  one  of  230  pages." 

And  Wallace  gives  this  account:  "In  February,  1858,  I 
was  suffering  from  a  rather  severe  attack  of  intermittent  fever 
at  Temate,  in  the  Moluccas;  and  one  day,  while  lying  on 
my  bed  during  the  cold  fit,  wrapped  in  blankets,  though  the 
thermometer  was  at  ^^°  Fahr.,  the  problem  again  presented 
itself  to  me,  and  something  led  me  to  think  of  the  'positive 


436 


BIOLOGY    AND    ITS    MAKERS 


checks'  described  by  Malthus  in  his  Essay  on  Population , 
a  work  I  had  read  several  years  before,  and  which  had  made 
a  deep  and  permanent  impression  on  my  mind.  These 
checks — war,  disease,  famine,  and  the  Hke — must,  it  occurred 
to  me,  act  on  animals  as  well  as  man.     Then  I  thought  of 


Fig.  1 20. — Alfred  Russel  Wallace,  1823-1913. 


the  enormously  rapid  multiplication  of  animals,  causing  these 
checks  to  be  much  more  effective  in  them  than  in  the  case  of 
man;  and  while  pondering  vaguely  on  this  fact,  there  sud- 
denly flashed  upon  me  the  idea  of  the  survival  of  the  fittest — 
that  the  individuals  removed  by  these  checks  must  be  on  the 


RISE    OF    EVOLUTIONARY   THOUGHT  437 

whole  inferior  to  those  that  survived.  In  the  two  hours  that 
elapsed  before  my  ague  fit  was  over,  I  had  thought  out 
almost  the  whole  of  the  theory;  and  the  same  evening  I 
sketched  the  draught  of  my  paper,  and  in  the  two  succeeding 
evenings  wrote  it  out  in  full,  and  sent  it  by  the  next  post  to 
Mr.  Darwin." 

It  thus  appears  that  the  announcement  of  the  Darwin- 
Wallace  theory  of  natural  selection  was  made  in  1858,  and 
in  the  following  year  was  published  the  book,  the  famous 
Origin  oj  Species,  upon  which  Darwin  had  been  working 
when  he  received  Mr.  Wallace's  essay.  Darwin  spoke  of  this 
work  as  an  outline,  a  sort  of  introduction  to  other  works 
that  were  in  the  course  of  preparation.  His  subsequent 
works  upon  Animals  and  Plants  under  Domestication,  The 
Descent  oj  Man,  etc.,  etc.,  expanded  his  theory,  but  none  of 
them  effected  so  much  stir  in  the  intellectual  world  as  the 
Origin  oj  Species. 

This  skeleton  outline  should  be  filled  out  by  reading 
Darwin^ s  Lije  and  Letters,  by  his  son,  and  the  complete 
papers  of  Darwin  and  Wallace,  as  originally  published  in 
the  Journal  oj  the  Linncean  Society.  The  original  papers 
are  reproduced  in  the  Popular  Science  Monthly  for  Novem- 
ber, 1 90 1. 

Wallace  was  born  in  1823,  and  died  Nov.  7,  1913.  He 
shares  with  Darwin  the  credit  of  propounding  the  theory  of 
natural  selection,  and  he  is  notable  also  for  the  publication  of 
important  books,  as  the  Malay  Archipelago,  The  Geographical 
Distribution  of  Animals,  The  Wonderful  Century,  etc. 

The  Spread  of  the  Doctrine  of  Organic  Evolution.    Hux- 
ley.— Darwin  was  of  a  quiet  habit,  not  aggressive  in  the 
defense  of  his  views.    His  theory  provoked  so  much  oppo- 
sition that  it  needed  some  defenders  of  the  pugnacious  type, 
^fc     In  England  such  a  man  was  found  in  Thomas  Henry  Huxley 
^H     (1825-1895).    He  was  one  of  the  greatest  popular  exponents 

L 


438 


BIOLOGY    AND    ITS    MAKERS 


of  science  of  the  nineteenth  century;  a  man  of  most  thorough 
and  exact  scholarship,  with  a  keen,  analytical  mind  that  went 
directly  to  the  center  of  questions  under  consideration,  and 
powers  as  a  writer  that  gave  him  a  wide  circle  of  readers. 
He  was  magnificently  sincere  in  his  fight  for  the  prevalence 


Fig.   121. — Thomas  Henry  Huxley,   1825-1895. 


of  intellectual  honesty.     Doubtless  he  will  be  longer  remem- 
bered for  this  service  than  for  anything  else. 

He  defended  the  doctrine  of  evolution,  not  only  against 
oratorical  attacks  like  that  of  Bishop  Wilberforce,  but  against 
well-considered  arguments  and  more  worthy  opponents.  He 
advanced  the  standing  of  the  theory  in  a  less  direct  w^ay 
by  urging  the  pursuit  of  scientific  studies  by  high-school 
and  university  students,  and  by  bringing  science  closer  to 


RISE    OF    EVOLUTIONARY    THOUGHT  439 

the  people.  He  was  a  pioneer  in  the  laboratory  teaching  of 
biology,  and  his  Manual  has  been,  ever  since  its  publica- 
tion in  1874,  the  inspiration  and  the  model  for  writers  of 
directions  for  practical  work  in  that  field. 

It  is  not  so  generally  known  that  he  was  also  a  great 
investigator,  producing  a  large  amount  of  purely  technical 
researches.  After  his  death  a  memorial  edition  of  his  scien- 
tific memoirs  was  published  in  four  large  quarto  volumes. 
The  extent  of  his  scientific  output  when  thus  assembled  was 
a  surprise  to  many  of  his  co-workers  in  the  field  of  science. 
His  other  writings  of  a  more  general  character  have  been 
collected  in  fourteen  volumes.  Some  of  the  essays  in 
this  collection  are  models  of  clear  and  vigorous  English 
style.  Mr.  Huxley  did  an  astonishing  amount  of  scientific 
work,  especially  in  morphology  and  palaeontology.  Those 
who  have  been  privileged  to  look  over  his  manuscripts  and 
unpublished  drawings  in  his  old  room  at  South  Kensington 
could  not  fail  to  have  been  impressed,  not  only  with  the 
extent,  but  also  with  the  accuracy  of  his  work.  Taking 
Johannes  Miiller  as  his  exemplar,  he  investigated  animal 
organisms  with  a  completeness  and  an  exactness  that  have 
rarely  been  equaled. 

An  intimate  account  of  his  life  will  be  found  in  The  Life 
and  Letters  oj  Thomas  Henry  LLuxley,  by  his  son. 

Haeckel. — Ernst  Haeckel,  of  Jena,  bom  in  1834  (Fig.  122), 
was  one  of  the  earliest  in  Germany  to  take  up  the  de- 
fense of  Darwin's  hypothesis.  As  early  as  1866  he  applied 
the  doctrine  of  evolution  to  all  organisms  in  his  Generelle 
Morphologie.  This  work,  which  has  been  long  out  of  print, 
represents  his  best  contribution  to  evolutionary  thought. 
He  has  written  widely  for  general  readers,  and  although  his 
writings  are  popularly  believed  to  represent  the  best  scientific 
thought  on  the  matter,  those  written  for  the  general  public 
are  not  regarded  by  most  biologists  as  strictly  representative. 


440 


BIOLOGY   AND    ITS    MAKERS 


As  a  thinker  he  is  more  careless  than  Huxley,  and  as  a  result 
less  critical  and  exact  as  a  writer. 

There  can  be  no  doubt  that  the  germs  of  evolutionary 
thought  existed  in   Greek  philosophy,  and  that  they  were 


Fig.   122. — Ernst  Haeckel,  Born   1834. 

retained  in  a  state  of  low  vitality  among  the  mediaeval  thinkers 
who  reflected  upon  the  problem  of  creation.  It  was  not, 
however,  until  the  beginning  of  the  nineteenth  century  that, 
under  the  nurture  of  Lamarck,  they  grew  into  what  we  may 
speak  of  as  the  modern  theory  of  evolution.  After  various 
vicissitudes  this  doctrine  was  made  fertile  by  Darwin,  who 
supplied  it  with  a  new  principle,  that  of  natural  selection. 

The  fruits  of  this  long  growth  are  now  being  gathered. 
After  Darwin  the  problem  of  biology  became  not  merely 
to  describe  phenomena,  but  to  explain  them.     This  is  the 


RISE    OF    EVOLUTIONARY    THOUGHT  441 

outcome  of  the  rise  and  progress  of  biology :  first,  crude  and 
uncritical  observations  of  the  forms  of  animated  nature; 
then  descriptive  analysis  of  their  structure  and  development; 
and,  finally,  experimental  studies,  the  effort  to  explain  vital 
phenomena,  an  effort  in  which  biologists  are  at  present  en- 
gaged. 


CHAPTER  XX 

RETROSPECT  AND  PROSPECT.     RECENT   TENDEN 
CIES  IN  BIOLOGY 

When  one  views  the  progress  of  biology  in  retrospect,  the 
broad  truth  stands  out  that  there  has  been  a  continuity  of 
development  in  biological  thought  and  interpretation.  The 
new  proceeds  out  of  the  old,  but  is  genetically  related  to  it. 
A  good  illustration  of  this  is  seen  in  the  modified  sense  in 
which  the  theories  of  epigenesis  and  pre-formation  have  been 
retained  in  the  biological  philosophy  of  the  nineteenth  cen- 
tury. The  same  kind  of  question  that  divided  the  philos- 
ophers of  the  seventeenth  and  eighteenth  centuries  has 
remained  to  vex  those  of  the  nineteenth;  and,  although  both 
processes  have  assumed  a  different  aspect  in  the  light  of  ger- 
minal continuity,  the  theorists  of  the  last  part  of  the  nineteenth 
century  were  divided  in  their  outlook  upon  biological  proc- 
esses into  those  of  the  epigenetic  school  and  those  who  are 
persuaded  of  a  pre-organization  in  the  germinal  elements  of 
organisms.  Leading  biological  questions  were  warmly  dis- 
cussed from  these  different  points  of  view. 

In  its  general  character  the  progress  of  natural  science 
has  been,  and  still  is,  a  crusade  against  superstition;  and  it 
may  be  remarked  in  passing  that  ''  the  nature  of  superstition 
consists  in  a  gross  misunderstanding  of  the  causes  of  nat- 
ural phenomena."  The  struggle  has  been  more  marked  in 
biology  than  in  other  departments  of  science  because  biology 
involves  the  consideration  of  living  organisms  and  undertakes 

442 


RECENT   TENDENCIES    IN    BIOLOGY  443 

to  establish  the  same  basis  for  thinking  about  the  organization 
of  the  human  body  as  about  the  rest  of  the  animal  series. 

The  first  triumph  of  the  scientific  method  was  the  over- 
throw of  authority  as  a  means  of  ascertaining  truth  and  sub- 
stituting therefor  the  method  of  observation  and  experiment. 
This  carries  us  back  to  the  days  of  Vesalius  and  Harvey, 
before  the  framework  of  biology  was  reared.  But  the  scien- 
tific method,  once  established,  led  on  gradually  to  a  belief  in 
the  constancy  of  nature  and  in  the  prevalence  of  universal 
laws  in  the  production  of  all  phenomena.  In  its  progress 
biology  has  exhibited  three  phases  which  more  or  less 
overlap:  The  first  was  the  descriptive  phase,  in  which 
the  obvious  features  of  animals  and  plants  were  merely 
described;  the  descriptive  was  supplemented  by  the  com- 
parative method;  this  in  due  course  by  the  experimental 
method,  or  the  study  of  the  processes  that  take  place  in 
organisms.  Thus,  description,  comparison,  and  experiment 
represent  the  great  phases  of  biological  development. 

The  Notable  Books  of  Biology  and  their  Authors.— The 
progress  of  biology  has  been  owing  to  the  efforts  of  men  of 
very  human  qualities,  yet  each  with  some  special  distinguish- 
ing feature  of  eminence.  Certain  of  their  publications  are 
the  mile-stones  of  the  way.  It  may  be  worth  while,  therefore, 
in  a  brief  recapitulation  to  name  the  books  of  widest  general 
influence  in  the  progress  of  biology.  Only  those  publica- 
tions will  be  mentioned  that  have  formed  the  starting-point 
of  some  new  movement,  or  have  laid  the  foundation  of  some 
new  theory. 

Beginning  with  the  revival  of  learning,  the  books  of 
Vesalius,  De  Corporis  Humani  Fabrica  (1543),  and  Harvey, 
De  Motii  Cordis  et  Sanguinis  (1628),  laid  the  foundations  of 
scientific  method  in  biology. 

The  pioneer  researches  of  Malpighi  on  the  minute  anat- 
omy of  plants  and  animals,  and  on  the  development  of  the 


444  BIOLOGY   AND    ITS    MAKERS 

chick,  best  represent  the  progress  of  investigation  between 
Harvey  and  Linnaeus.  The  three  contributions  referred  to 
are  those  on  the  Anatomy  of  Plants  {Anatome  Plantarum, 
1675-1679);  on  the  Anatomy  of  the  Silkworm  {De  Bomhyce^ 
1669) ;  and  on  the  Development  oj  the  Chick  {De  Formatione 
Pulli  in  Ovo  and  De  Ovo  Incubato,  both  1672). 

We  then  pass  to  the  Systema  Naturce  (twelve  editions, 
1 735-1 768)  of  Linnaeus,  a  work  that  had  such  wide  in- 
fluence in  stimulating  activity  in  systematic  botany  and 
zoology. 

Wolff's  Theoria  Generationis,  1759,  and  his  De  Formatiofie 
Intestinorumy  1764,  especially  the  latter,  were  pieces  of 
observation  marking  the  highest  level  of  investigation  of 
development  prior  to  that  of  Pander  and  Von  Baer. 

Cuvier,  in  Le  Rbgne  Animal ^  18 16,  applied  the  principles 
of  comparative  anatomy  to  the  entire  animal  kingdom. 

The  publication  in  1800  of  Bichat's  Traite  des  Membraftes 
created  a  new  department  of  anatomy,  called  histology. 

Lamarck's  book.  La  Philosophie  Zoologique,  1809,  must 
have  a  place  among  the  great  works  in  biology.  Its  influence 
was  delayed  for  more  than  fifty  years  after  its  publication. 

The  monumental  work  of  Von  Baer  on  Development 
{Ueber  Entwicklungsgeschichie  der  Thiere),  1828,  is  an  almost 
ideal  combination  of  observation  and  conclusion  in  embry- 
ology. 

The  Microscopische  Untersuchungen,  1839,  of  Schwann 
marks  the  foundation  of  the  cell-theory. 

The  Handbook  of  Johannes  Muller  {Handbuch  der 
Physiologie  des  Menschen),  1846,  remains  unsurpassed  as  to 
its  plan  and  its  execution. 

Max  Schultze  in  his  treatise  Ueber  Muskelkorperchen  und 
das  was  man  eine  Zelle  zu  nennen  habe,  186 1,  established  one 
of  the  most  important  conceptions  with  which  biology  has 
been  enriched,  viz.,  the  protoplasm  doctrine.  ' 


RECENT   TENDENCIES    IN    BIOLOGY  445 

Darwin's  Origin  of  Species,  1859,  is,  from  our  present 
outlook,  the  greatest  classic  in  biology. 

Pasteur's  Studies  on  Fermentation,  1876,  is  typical  of  the 
quality  of  his  work,  though  his  later  investigations  on  in- 
oculations for  the  prevention  of  hydrophobia  and  other 
maladies  are  of  greater  importance  to  mankind. 

Ii  is  somewhat  puzzling  to  select  a  man  to  represent  the 
study  of  fossil  life,  one  is  tempted  to  name  E.  D.  Cope, 
whose  researches  were  conceived  on  the  highest  plane. 
Zittel,  however,  covered  the  entire  field  of  fossil  life,  and  his 
Handbook  of  Palceontology  is  designated  as  a  mile-post  in  the 
development  of  that  science. 

Before  the  Renaissance  the  works  of  Aristotle  and  Galen 
should  be  included. 

From  the  view-point  suggested,  the  more  notable  figures  in 
the  development  of  biology  are:  Aristotle,  Galen,  Vesalius, 
Harvey,  Malpighi,  Linnaeus,  Wolff,  Cuvier,  Bichat,  Lamarck, 
Von  Baer,  J.  Miiller,  Schwann^  Schultze,  Darwin,  Pasteur, 
and  Zittel. 

Such  a  list  is,  as  a  matter  of  course,  arbitrary,  and  can 
serve  no  useful  purpose  except  that  of  bringing  into  com- 
bination in  a  single  group  the  names  of  the  most  illustrious 
founders  of  biological  science.  The  individuals  mentioned 
are  not  all  of  the  same  relative  rank,  and  the  list  should  be 
extended  rather  than  contracted.  Schwann,  when  the  entire 
output  of  the  two  is  considered,  would  rank  lower  as  a  scien- 
tific man  than  Koelliker,  who  is  not  mentioned,  but  the 
former  must  stand  in  the  list  on  account  of  his  connection 
with  the  cell-theory.  Virchow,  the  presumptive  founder  of 
pathology,  is  omitted,  as  are  also  investigators  like  Koch, 
whose  line  of  activity  has  been  chiefly  medical. 

Recent  Tendencies  in  Biology.  Higher  Standards. — In 
attempting  to  indicate  some  of  the  more  evident  influences 
that  dominate  biological  investigation  at  the  present  time;, 


446  BIOLOGY   AND    ITS    MAKERS 

nothing  more  than  an  enumeration  of  tendencies  with  a 
running  commentary  is  possible.  One  notes  first  a  whole- 
some influence  in  the  establishment  of  higher  standards,  both 
of  research  and  of  scientific  publication.  Investigations  as  a 
whole  have  become  more  intensive  and  more  critical.  Much 
of  the  work  that  would  have  passed  muster  for  publication 
two  decades  ago  is  now  regarded  by  the  editors  of  the  best 
biological  periodicals  as  too  general  and  too  superficial.  The 
requisites  for  the  recognition  of  creditable  work  being  higher, 
tends  to  elevate  the  whole  level  of  biological  science. 

Improvement  in  Tools  and  Methods. — This  has  come 
about  partly  through  improvement  in  the  tools  and  in  the 
methods  of  the  investigators.  It  can  hardly  be  said,  however, 
that  thinking  and  discernment  have  been  advanced  at  the 
same  rate  as  the  mechanical  helps  to  research.  In  becoming 
more  intensive,  the  investigation  of  biological  problems  has 
lost  something  in  comprehensiveness.  That  which  some  of 
the  earlier  investigators  lacked  in  technique  was  compensated 
for  in  the  breadth  of  their  preliminary  training  and  in  their 
splendid  appreciation  of  the  relations  of  the  facts  at  their 
disposal. 

The  great  improvement  in  the  mechanical  adjustments 
and  in  the  optical  powers  of  microscopes  has  made  it  possible 
to  see  more  regarding  the  physical  structure  and  the  activities 
of  organisms  than  ever  before.  Microtomes  of  the  best  work- 
manship have  placed  in  the  hands  of  histologists  the  means 
of  making  serial  sections  of  remarkable  thmness  and  regular- 
ity. 

The  great  development  of  micro-chemical  technique  also 
has  had  the  widest  influence  in  promoting  exact  researches 
in  biology.  Special  staining  methods,  as  those  of  Golgi 
and  Bethe,  by  means  of  which  the  wonderful  fabric  of  the 
nervous  system  has  been  revealed,  are  illustrations. 

The  separation  by  maceration  and  smear  preparation  of  en- 


RECENT   TENDENCIES    IN    BIOLOGY  447 

tire  histological  elements  so  that  they  may  be  viewed  as  solids 
has  come  to  supplement  the  study  of  sections.  Reconstruc- 
tion, by  carving  wax  plates  of  known  thickness  into  the  form 
of  magnified  sections  drawn  upon  their  surfaces  to  a  scale, 
and  then  fitting  the  plates  together,  has  been  very  helpful  in 
picturing  complicated  anatomical  relations.  This  method 
has  made  it  possible  to  produce  permanent  vv^ax  models  of 
minute  structures  magnified  to  any  desired  degree.  Minute 
dissections,  although  not  yet  sufficiently  practiced,  are  never- 
theless better  than  the  wax  models  for  making  accurate 
drawings  of  minute  structures  as  seen  in  relief. 

The  injection  of  the  blood-vessels  of  extremely  small 
embryos  has  made  it  possible  to  study  advantageously  the 
circulatory  system.  The  softening  of  bones  by  acid  after 
the  tissues  are  already  embedded  in  celloidin  has  offered  a 
means  of  investigating  the  structure  of  the  internal  ear  by 
sections,  and  is  widely  applicable  to  other  tissues. 

With  the  advantage  of  the  new  appliances  and  the  new 
methods,  the  old  problems  of  anatomy  are  being  worked  over 
on  a  higher  level  of  requirement.  Still,  it  is  doubtful  whether 
even  the  old  problems  will  be  solved  in  more  than  a  relative 
way.  It  is  characteristic  of  the  progress  of  research  that  as 
one  proceeds  the  horizon  broadens  and  new  questions  spring 
up  in  the  pathway  of  the  investigator.  He  does  not  solve 
the  problems  he  sets  out  to  solve,  but  opens  a  lot  of  new  ones. 
This  is  one  of  the  features  of  scientific  research  that  make 
its  votaries  characteristically  optimistic. 

Experimental  Work. — Among  the  recent  influences  tend- 
ing to  advance  biology,  none  is  more  important  than  the  ap- 
plication of  experiments  to  biological  studies.  The  exper- 
imental method  is  in  reahty  applicable  to  diverse  fields  of 
biological  research,  and  its  extensive  use  at  present  indicates 
a  movement  in  the  right  direction ;  that  is,  a  growing  interest 
in  the  study  of  processes.     One  of  the  earliest  problems  of 


448  BIOLOGY   AND    ITS    MAKERS 

the  biologist  is  to  investigate  the  architecture  of  Hving  beings; 
then  there  arise  questions  as  to  the  processes  that  occur  within 
the  organism,  and  the  study  of  processes  involves  the  employ- 
ment of  experiments.  In  the  pursuit  of  physiology  exper- 
iments have  been  in  use  since  the  time  of  Harvey,  but  even 
in  that  science,  v^here  they  are  indispensable,  experiments 
did  not  become  comparative  until  the  nineteenth  century. 
It  now  appears  that  various  forms  of  experiment  give  also 
a  better  insight  into  the  structure  of  organisms,  and  the  prac- 
tice of  applying  experiments  to  structural  studies  has  given 
rise  to  the  new  department  of  experimental  morphology. 

For  the  purpose  of  indicating  some  of  the  directions  in 
which  biology  has  been  furthered  by  the  experimental  method 
of  investigation,  we  designate  the  fields  of  heredity  and  evo- 
lution, changes  in  the  environment  of  organisms,  studies  on 
fertilization  and  on  animal  behavior. 

The  recognition  that  both  heredity  and  the  process  of 
evolution  can  be  subjected  to  experimental  tests  was  a  revela- 
tion. Darwin  and  the  early  evolutionists  thought  the  evolu- 
tionary changes  too  slow  to  be  appreciated,  but  now  we 
know  that  many  of  the  changes  can  be  investigated  by 
experiment.  Numerous  experiments  on  heredity  in  poultry 
(Davenport),  in  rats,  in  rabbits,  and  in  guinea-pigs  (Castle) 
have  been  carried  out — experiments  that  test  the  laws  of 
ancestral  inheritance  and  throw  great  light  upon  the  ques- 
tions introduced  by  the  investigations  of  Mendel  and  De 
Vries.  The  investigations  of  De  Vries  on  the  evolution  of 
plant-life  occupy  a  notable  position  among  the  experimental 
studies. 

A  large  number  of  experiments  on  the  effects  produced 
by  changes  in  the  external  conditions  of  life  have  been  made. 
To  this  class  of  investigations  belong  studies  on  the  regulation 
of  form  and  function  in  organisms  (Loeb,  Child),  the  effects 
produced  by  altering  mechanical  conditions  of  growth,  by 


RECENT   TENDENCIES    IN    BIOLOGY  449 

changing  the  chemical  environment,  etc.  There  is  some 
internal  mechanism  in  living  matter  that  is  influenced  by 
changes  in  external  conditions,  and  the  study  of  the  regulation 
of  the  internal  processes  that  produce  form  and  structure 
have  given  rise  to  a  variety  of  interesting  problems.  The 
regeneration  of  lost  parts  and  regeneration  after  intention- 
ally-imposed injury  has  received  much  attention  (Morgan). 
Marine  animals  are  especially  amenable  to  manipulations  of 
this  nature,  as  well  as  to  alterations  in  their  surroundings, 
on  account  of  the  ease  in  altering  the  chemical  environment 
in  which  they  live.  The  latter  may  be  accomplished  by 
dissolving  harmless  chemical  salts  in  the  sea-water,  and 
observing  the  changes  produced  by  the  alterations  of  the 
surrounding  conditions.  By  this  means  Herbst  and  others 
have  produced  very  interesting  results. 

In  the  field  of  artificial  fertilization,  free  swimming  larvae 
have  been  raised  from  eggs  artificially  fertilized  by  changes 
in  osmotic  pressure,  and  also  by  treating  them  with  both 
organic  and  inorganic  acids;  and  these  studies  have  greatly 
altered  opinion  regarding  the  nature  of  fertilization,  and  of 
certain  other  phenomena  of  development. 

Animal  Behavior. — The  study  of  animal  behavior  (Jen- 
nings) is  a  very  characteristic  activity  of  the  present,  in  which 
certain  psychological  processes  are  investigated.  These  in- 
vestigations have  given  rise  to  a  distinct  line  of  research  par- 
ticipated in  by  psychologists  and  biologists.  The  study  of 
the  way  in  which  animals  will  react  toward  light  of  different 
colors,  to  variations  in  the  intensity  of  light,  to  alterations  in 
temperature,  and  to  various  other  forms  of  stimuli  are  yield- 
ing very  important  results,  that  enable  mvestigators  to  look 
beneath  the  surface  and  to  make  important  deductions 
regarding  the  nature  of  psychological  processes. 

A  line  closely  allied  to  experimentation  is  the  application 
of  statistics  to  biological  processes,  such  as  those  of  growth, 


450  BIOLOGY   AND    ITS    MAKERS 

Stature,  the  law  of  ancestral  inheritance,  the  statistical  study 
of  variations  in  spines,  markings  on  shells,  etc.,  etc.  (Galton, 
Pearson,  Davenport). 

Other  branches  of  biology  that  have  been  greatly  devel- 
oped by  the  experimental  method  are  those  of  bacteriology 
and  physiological  chemistry.  The  advances  in  the  latter 
have  greatly  widened  the  horizon  of  our  view  regarding  the 
nature  of  vital  activities,  and  they  compose  one  of  the  leading 
features  of  current  biological  investigation. 

Some  Tendencies  in  Anatomical  Studies.  Cell-Lineage. — 
While  experimental  work  occupies  the  center  of  the  stage, 
at  the  same  time  great  improvements  in  morphological 
studies  are  evident.  It  will  be  only  possible,  however,  to 
indicate  in  a  general  way  the  direction  in  which  investigations 
are  moving.  We  note,  first,  as  in  a  previous  paragraph,  that 
the  improvement  in  morphology  is  generic  as  well  as  specific. 
Anatomical  analysis  is  being  carried  to  its  limits  in  a  number 
of  directions.  The  investigations  that  are  connected  with 
the  study  of  cells  afford  a  conspicuous  illustration  of  this 
fact.  Studies  in  cell-lineage  have  led  to  an  exact  determina- 
tion of  cell-succession  in  the  development  of  certain  animals, 
and  such  studies  are  still  in  progress.  Great  progress  also 
has  been  made  in  the  study  of  physical  structure  of  living 
matter.  The  tracing  of  cell-lineage  is  a  feat  of  remarkably 
accurate  and  patient  work.  But,  however  much  this  may 
command  our  admiration,  it  has  been  surpassed  (as  related 
in  Chapter  XI)  by  investigations  regarding  the  organization 
of  the  egg  and  the  analysis  of  chromosomes.  Boveri,  Conk- 
lin,  Wilson,  and  others  have  shown  that  there  are  recognizable 
areas  within  the  protoplasm  of  the  egg  that  have  a  definite 
historical  relationship  to  certain  structures  in  process  of 
development.  This  is  the  basis  upon  which  rests  the  doctrine 
of  pre-localization  of  tissue- forming  substances  within  the 
protoplasm  of  the  egg. 


RECENT   TENDENCIES    IN    BIOLOGY  451 

Anatomy  of  the  Nervous  System. — In  another  direction 
the  progress  of  anatomical  studies  is  very  evident,  that  is, 
investigations  of  the  nervous  system  and  the  sense-organs. 
The  wonderfully  complicated  relations  of  nerve  elements 
have  been  worked  out  by  Ramon  y  Cajal.  The  studies  of 
Hodge  and  others  upon  optical  changes  occurring  within  the 
cells  of  the  nervous  system  owing  to  their  functional  activity 
have  opened  a  great  field  for  investigation.  The  studies  of 
Strong,  Herrick,  and  others  upon  the  distribution  of  nerve- 
components  in  the  nerves  of  the  head  and  the  investigations 
of  Harrison  on  the  growth  and  the  regeneration  of  nerve- 
fibers  give  illustrations  of  current  tendencies  in  biological 
investigation.  The  analysis  of  the  central  nervous  system 
into  segmental  divisions  on  the  basis  of  functional  activity 
(Johnston)  is  still  another  illustration. 

The  Application  of  Biological  Facts  to  the  Benefit  of  Man- 
kind.— The  practical  application  of  biology  to  the  benefit 
of  mankind  is  a  striking  feature  of  present-day  tendencies. 
The  activity  set  on  foot  by  the  researches  of  Pasteur,  Koch, 
and  others  has  created  a  department  of  technical  biology  of 
the  greatest  importance  to  the  human  race. 

Under  the  general  heading  should  be  included  tne  demon- 
stration of  the  connection  between  insects  and  the  propagation 
of  yellow  fever,  malaria,  and  other  disorders;  and  as  an  illus- 
tration of  activity  in  1907,  we  think  of  the  commission  recently 
appointed  to  investigate  the  terrible  scourge  of  the  sleeping- 
sickness  which  has  been  prevalent  in  Africa.  Here  also  we 
would  group  studies  of  a  pathological  character  on  blood- 
immunity,  toxin  and  antitoxin,  also  studies  on  the  inoculation 
for  the  prevention  of  various  diseases  that  affect  animals  and 
mankind.  Very  much  benefit  has  already  accrued  from  the 
practical  application  of  biological  researches  of  this  nature, 
which,  in  reality,  are  still  in  their  infancy. 

We  find  the  application  of  biological  facts  to  agriculture 


452  BIOLOGY    AND    ITS    MAKERS 

in  the  form  of  soil-inoculation,  in  the  tracing  of  the  sources 
of  nitrates  in  the  soil,  and  studies  of  the  insects  injurious  to 
vegetation;  their  further  application  to  practical  forestry, 
and  in  sanitary  sciences.  This  kind  of  research  is  also  ap- 
plied to  the  study  of  food-supply  for  fishes,  as  >n  the  case  of 
Plankton  studies. 

The  Establishment  and  Maintenance  of  Biological  Lab- 
oratories.— The  establishment  of  seaside  biological  observa- 
tories and  various  other  stations  for  research  have  had  a  great 
influence  on  the  development  of  biology.  The  most  famous 
biological  station  is  that  founded  at  Naples  (Fig.  123)  in  1872 
by  Anton  Dohrn,  and  it  is  a  gratification  to  biologists  to 
know  that  he  still  remains  its  director.  This  international 
station  for  research  has  stimulated,  and  is  at  present  stim- 
ulating, the  growth  of  biology  by  providing  the  best  condi- 
tions for  carrying  on  researches  and  by  the  distribution  of 
material  which  has  been  put  up  at  the  seacoast  by  the  most 
skilled  preservators.  There  are  many  stations  modeled 
after  that  at  Naples.  The  Marine  Biological  Laboratory 
at  Woods  Holl,  Mass.,  is  of  especial  prominence,  and 
the  recently  reorganized  Wistar  Institute  of  Anatomy  at 
Philadelphia  is  making  a  feature  of  the  promotion  of  ana- 
tomical researches,  especially  those  connected  with  the  anat- 
omy of  the  nervous  system. 

Laboratories  similar  to  those  at  the  seaside  have  been 
established  on  several  fresh-water  lakes.  The  studies  carried 
on  in  those  places  of  the  complete  biology  of  lakes,  taking 
into  account  the  entire  surroundings  of  organisms,  are  very 
interesting  and  important. 

Under  this  general  head  should  be  mentioned  stations 
under  the  control  of  the  Carnegie  Institution,  the  various 
scientific  surveys  under  the  Government,  and  the  United  States 
Fish  Commission,  which  carries  on  investigations  in  the  bi- 
ology of  fishes  as  well  as  observations  that  affect  their  use 


a, 


'o 
1 


454  BIOLOGY    AND    ITS    MAKERS 

as  articles  of  diet.  The  combined  output  of  the  various 
laboratories  and  stations  of  this  nature  is  very  considerable, 
and  their  influence  upon  the  progress  of  biology  is  properly 
included  under  the  head  of  present  tendencies. 

The  organization  of  laboratories  in  our  great  universities 
and  their  product  exercise  a  wide  influence  on  the  progress  of 
biology,  that  science  having  within  twenty-five  years  come  to 
occupy  a  position  of  great  importance  among  the  subjects  of 
general  education. 

Establishment  and  Maintenance  of  Technical  Periodicals. 
— It  is  manifestly  very  important  to  provide  means  for  the 
publication  of  results  and,  as  needed,  to  have  technical 
periodicals  established  and  properly  maintained.  Their 
maintenanc-e  can  not  be  effected  on  a  purely  commercial 
basis,  and  the  result  is  that  some  of  our  best  periodicals  re- 
quire financial  assistance  in  order  to  exist  at  all.  The  sub- 
sidizing and  support  of  these  periodicals  aid  materially  in 
the  biological  advance.  A  typical  technical  periodical  is 
Schultze's  famous  Archiv  filr  Mikroscopische  Anatomiey 
founded  in  1864  by  Schultze  and  continued  to  the  present 
time.  Into  its  pages  go  the  highest  grade  of  investigations, 
and  its  continued  existence  has  a  salutary  influence  upon  the 
progress  of  biology.  The  list  of  technical  periodicals  would 
be  too  long  to  name,  but  among  others  the  Morphologisches 
Jahrhuch  of  Gegenbaur,  and  Koelliker's  Zeitschrijt  jilrWissen- 
schajtliche  Zoologie  have  had  wide  influence.  In  England 
the  Quarterly  Journal  of  Microscopical  Science  is  devoted  to 
morphological  investigations,  while  physiology  is  provided 
for  in  other  journals,  as  it  is  also  in  Germany  and  other 
countries.  In  the  United  States  the  Journal  oj  Morphology ^ 
passed  through  seventeen  volumes  under  the  editorship  of 
C.  O.  Whitman  (1842-1910)  and  was  maintained  on  the  high- 
est plane  of  scholarship.  The  fine  execution  of  the  plates 
also  and  the  high  grade  of  typographical  work  gave  this 


RECENT  TENDENCIES   IN   BIOLOGY  455 

Journal  a  place  among  the  best  published  scientific  periodicals. 
After  a  period  of  cessation  the  publication  of  the  Journal 
of  Morphology  was  resumed.  In  the  meantime,  the  A  merican 
Journal  of  Anatomy  had  entered  nearly  the  same  field,  and 
these  two  give  wider  opportunity  for  publication  of  the  increas- 
ing number  of  researches  in  morphology  by  American  investi- 
gators. In  the  department  of  experimental  work  many  jour- 
nals have  sprung  up,  as  Biometrica,  edited  by  Karl  Pearson, 
Roux's  Archiv  fur  Entwicklungs-Mechanik,  the  Journal  of 
Experimental  Zoology  recently  established  in  the  United 
States,  etc.,  etc. 

Exploration  of  the  Fossil  Records. — Explorations  of  the 
fossil  records  have  been  recently  carried  out  on  a  scale  never 
before  attempted,  involving  the  expenditure  of  large  sums, 
but  bringing  results  of  great  importance.  The  American 
Museum  of  Natural  History,  in  New  York  City,  has  carried 
on  an  extensive  survey,  which  has  enriched  it  with  wonderful 
collections  of  fossil  animals.  Besides  explorations  of  the 
fossil-bearing  rocks  of  the  Western  States  and  Territories, 
operations  in  another  locality  of  great  importance  are  con- 
ducted in  the  Fayiim  district  of  Egypt.  The  result  of  the 
studies  of  these  fossil  animals  is  to  make  us  acquainted  not 
only  with  the  forms  of  ancient  life,  but  with  the  actual  line 
of  ancestry  of  many  living  animals.  The  advances  in 
this  direction  are  most  niteresting  and  most  important. 
This  extensive  investigation  of  the  fossil  records  is  one  of  the 
present  tendencies  in  biology. 

Conclusion.  — ^In  brief,  the  chief  tendencies  in  current  bio- 
logical researches  are  mainly  included  under  the  following 
headings:  Experimental  studies  in  heredity,  evolution,  and  ani- 
mal behavior;  more  exact  anatomical  investigations,  especially 
in  cytology  and  neurology,  the  promotion  and  dissemination 
of  knowledge  through  biological  periodicals;  the  provision  of 
better  facilities  in  specially  equipped  laboratories,^  in  the 


456  BIOLOGY   AND    ITS   MAKERS 

application  of  results  to  the  benefit  of  mankind,  and  in  the 
investigation  of  the  fossil  records. 

The  atmosphere  of  thought  engendered  by  the  progress  of 
biology  is  beneficial  in  every  way.  While  its  progress  has 
dealt  the  death-blow  to  many  superstitions  and  changed 
materially  views  regarding  the  universe,  it  is  gratifying  to 
think  that  it  has  not  been  iconoclastic  in  its  influence,  but 
that  it  has  substituted  something  better  for  that  which  was 
taken  away.  It  has  given  a  broader  and  more  wholesome 
basis  for  religion  and  theories  of  ethics;  it  has  taught  greater 
respect  for  truth  and  morality.  However  beneficial  this 
progress  has  been  in  the  past,  who  can  doubt  that  the  mission 
of  biology  to  the  twentieth  century  will  be  more  important 
than  to  the  past,  and  that  there  will  be  embraced  in  its 
progress  greater  benefits  than  any  we  have  yet  known  ? 


READING    LIST 


The  books  and  articles  relating  to  the  history  of  biology  are  numerous. 
Those  designated  below  embrace  some  of  the  more  readily  accessible  ones. 
While  some  attention  has  been  given  to  selecting  the  best  sources,  no 
attempt  has  been  made  to  give  a  comprehensive  Hst. 


I.    GENERAL  REFERENCES 

CuviER.  Histoire  des  Sciences  Naturelles.  5  vols.,  1841-1S45.  Ex- 
cellent,    Written  from  examination  of  the  original  documents. 

Carus.  Geschichte  der  Zoologie,  1872.  Also  Histoire  de  la  Zoologie, 
1880.  A  work  of  scholarship.  Contains  excellent  account  of  the 
Physiologus. 

Sachs.  History  of  Botany,  1890.  Excellent.  Articles  in  the  Botanical 
Gazette  for  1895  supplement  his  account  by  giving  the  more  recent 
development  of  botany. 

White.  A  History  of  the  Warfare  of  Science  with  Theology  in  Christen- 
dom, 2  vols.,  1900.  Good  account  of  Vesalius  and  the  overthrow  of 
authority  in  science. 

Whewell.  History  of  the  Inductive  Sciences,  vol.  II,  1863.  Lacks 
insight  into  the  nature  of  biology  and  the  steps  in  its  progress.  Men- 
tioned because  so  generally  known. 

Williams.  A  History  of  Science,  5  vols.,  1904.  Finely  illustrated.  Con- 
tains many  defects  in  the  biological  part  as  to  the  relative  rank  of  the 
founders:  Vesalius  diminished,  Paracelsus  magnified,  etc.  Also,  the 
Story  of  Nineteenth  Century  Science,  1900.  Collected  articles  from 
Harper^ s  Magazine.     Good  portraits.     Uncritical  on  biological  matters. 

Thomson.  The  Science  of  Life,  1899.  An  excellent  brief  history  of 
biology. 

Foster.  Lectures  on  the  History  of  Physiology,  1901.  Fascinatingly 
written.  Notable  for  poise  and  correct  estimates,  based  on  the  use  of 
the  original  documents. 

Geddes.  a  Synthetic  Outhne  of  the  History  of  Biology.  Proc.  Roy.  Sac. 
Edinb.,  1885-1886.     Good. 

457 


45S  READING   LIST 

Richardson.     Disciples  of  ^sculapius,    2  vols.,  1901.     Collected  papers 

from    The   Asclepiad.     Sympathetic   accounts   of   Vesalius,  Malpighi, 

J.  Hunter,  and  others.     Good  illustrations. 
Lankester.     The  History  and  Scope  of    Zoology,  in  The  Advancement 

of  Science,  1890.     Good.     Same  article  in  Ency.  Brit,  under  the  title 

of  Zoology. 
Spencer.     Principles  of  Biology,  2  vols.,  1866. 
Hertwig.     The    Growth   of   Biology   in   the   Nineteenth    Century,   Ann. 

Rept.  Smithson.  Inst.,  1900. 
Buckle.     History  of  Civilization,  vol.  I,  second  edition,  1870. 
Macgilivray.     Lives  of  Eminent  Zoologists  from  Aristotle  to  Linnaeus. 
Merz.   a  History  of  P^uropean  Thought  in  the  Nineteenth  Century,  vol.  II, 

Scientific  Thought,  1903. 
RoUTLEDGE.     A  Popular  History  of  Science.     General  and  uncritical  as 

to  biology. 
HOEFER.     Histoire  de  la  Zoologie,  1873.     Not  very  good. 
Encyclopedia    Britannica.     Among  the  more    excellent    articles    arc: 

Biology    by  Huxley;    Protoplasm    by   Geddes;    History  of  Anatomy 

by  Turner. 
Chambers's    Encyclopaedia.     New     Edition.     Discerning     articles     by 

Thomson  on  the  Cell-theory,  by  Geddes  on  Biology,  Evolution. 
NouvELLE  Biographie  Generale.     Good  articles  on  the  older  writers. 

Often  unreliable  as  to  dates. 
Haeckel.     The  historical  chapters  in  The  Evolution  of  Man,  1892,  and 

Anthropogenic,  fifth  edition,  1903.     Good. 
Haeckel.     The  History  of  Creation,  vol.  I,  1884. 
Hertwig.     The  General  Survey  of  the  History  of    Zoology  in  his  Manual 

of  Zoology,  1902.     Brief  but  excellent. 
Parker  and  Has  well.     Text-book  of  Zoology,  1897.     Historical  chapter 

in  vol.  II.  , 

Nicholson.     Natural   History,   its   Rise   and   Progress   in  Britain,    1886. 

Also  Biology. 
Pettigrew.     Gallery  of  Medical  Portraits,  5  vols.     Contains  many  por- 
traits and  biographical  sketches  of  men  of  general  influence,  as  Bichat, 

Galen,  Malpighi,  etc. 
PUSCHMANN.     Handbuch  der  Geschichte  der  Medizin,  3  vols.     Good  for 

topics  in  anatomy  and  physiology. 
Baas.     The  History  of  Medicine,  1889. 
Radl.     Geschichte  der  Biologischen  Theorien  seit  dcm  Ende  des  Siebzehn- 

ten  Jahrhundert,  1905. 
Janus.     A   Periodical  devoted  to  the  history  of    medicine  and    natural 

science,  founded  in  1896. 
Zoologische  Annalen.     Founded  by  Max  Braun  in  1904  in  the  interests 

of  the  history  of  zoology. 


READING  LIST  459 

MiTTEILUNGEN   ZUR   GeSCHICHTE   DER   MeDIZIN   UND    NaTURWISSENSCHAF- 

TEN,  founded  1901. 

Studien  ZUR  Geschichte  DER  Medizin,  Edited  by  Karl  Sudhoflf.  Very 
important  additions  to  the  early  history  of  anatomy,  including  the  Ms. 
sources  as  well  as  the  earliest  printed  pictures  of  anatomy. 

Surgeon  General's  Library.  The  Catalogue  should  be  consulted  for 
its  many  biographical  references  to  biologists.  The  Library  is  es- 
pecially rich  in  historical  documents,  as  old  anatomies,  physiologies, 
zoologies,  etc. 

Evolution.  The  bibliography  of  Evolution  is  given  below  under  the 
chapters  dealing  with  the  evolution  theory. 


II.     SPECIAL   REFERENCES 

CHAPTER   I 

Ancient  BIOLOGICAL  Science :  Carus;  Botany  after  1530,  Sachs.  Aris- 
totle: Cuvier,  a  panegyric;  Lewes,  Aristotle — A  Chapter  from  the  History 
of  Science,  1864,  a  critical  study;  Huxley,  On  some  Mistakes  Attributed 
to  Aristotle;  Macgilivray;  Aristotle's  History  of  Animals  translated  in 
Bohn's  Classical  Library,  1887.  Pliny:  Magilivray;  Thorndike,  The 
Place  of  Magic  in  the  Intellectual  History  of  Europe,  1905,  chap.  III.  The 
Renaissance:  Symonds.  Epochs  in  Biological  History:  Geddes  (see 
General  List). 

CHAPTER   II 

Vesalius:  Roth,  Andreas  Vesalius  Bruxellensis,  the  edition  of  1892, 
the  standard  source  of  knowledge  of  Vesalius  and  his  times,  contains  bibli- 
ography, references  to  his  different  portraits,  the  resurrection  bone,  etc.,  etc.; 
Foster  (see  General  List),  Lecture  I,  excellent;  Richardson  in  Disciples  of 
yEsculapius,  vol.  I,  contains  pictures,  his  signature,  etc.;  Pettigrew;  White, 
vol.  II,  pp.  51-55;  The  Practitioner,  1896,  vol.  56;  The  Asclepiad,  1885, 
vol.  II;  De  Humani  Corporis  Fabrica,  editions  of  1543  and  1555;  Opera 
Omnia,  edited  by  Boerhaave,  2  vols.,  1725;  Anatomical  Illustration  before 
Vesalius,  Locy,  Journ.  Morphology,  1911.  Galen:  Pettigrew;  Huxley  in 
his  essay  on  William  Harvey. 

CHAPTER   III 

Harvey:  Foster,  Lecture  H,  with  quotations,  excellent;  Dalton,  History 
of  the  Circulation;  Huxley,  William  Harvey,  a  cn'tical  essays  Harvey's 
Works  translated  by  Willis,  with  biography,  Sydenham  Society,  1847;  Life 


460  READING    LIST 

of  Harvey  by  D'Arcy  Power,  1^98;  Brooks,  Harvey  as  Embryologist, 
Bull.  Johns  Hop.  Hospit.,  vol.  VIII,  1897,  good.  An  Anatomical  Disser- 
tation upon  the  Movement  of  the  Heart  and  Blood  in  Animals,  a  facsimile 
reproduction  of  the  first  edition  of  the  famous  De  Motu  Cordis  et  Sanguinis, 
1628.     Privately  reproduced  by  Dr.  Moreton  in  1894.     Very  interesting. 


CHAPTER   IV 

Hooke:  Biography  in  encyclopaedias,  his  microscope  in  Carpenter,  The 
Microscope  and  Its  Revelations,  8th  ed.,  1900. 

Malpighi:  Richardson,  vol.  II;  Same  article  in  The  Asclepiad,  vol.  X, 
1893;  Atti,  Life  and  Work,  in  Italian,  1847,  portrait;  Pettigrew,  vol.  II; 
Marcello  Malpighi  e  1' Opera  Sua,  1897,  a  collection  of  addresses  at  the 
unveiling  of  Malpighi's  monument  at  Crevalcuore,  that  by  Koelliker  ex- 
cellent; Locy,  Malpighi,  Swammerdam,  and  Leeuwenhoek,  Pop.  Sci.  Mo., 
1901 — protrait  and  pictures  from  his  works;  MacCallum,  /.  Hop.  Univ. 
Hospit.  Bull.  Malpighi's  Writings:  Opera  Omnia,  difficult  to  obtain, 
the  Robt.  Littlebuiy  edition,  Lond.,  1687,  contains  posthumous  papers  and 
"biography;  separate  works  not  uncommon;  Traite  du  Ver  a  Sole,  Mont- 
pellier,  1878,  contains  his  life  and  works. 

Swammerdam:  Life  by  Boerhaave  in  BibHa  Naturae,  1737;  also  Bibel 
der  Natur,  1752;  also  The  Book  of  Nature,  1758;  Von  Baer,  Johann 
Swammerdam' s  Leben  und  Verdienste  um  die  Wissenschaft,  1864,  in 
Reden,  vol.  I;  Locy,  loc.  cit. — portrait. 

Leeuwenhoek:  New  biographical  facts  in  Richardson,  vol.  I,  p.  108; 
same  article  in  The  Asclepiad,  vol.  II,  1885,  portrait,  signature,  and  other 
illustrations;  Arcana  Naturae;  Selected  works  in  English,  1758;  Locy, 
Pop.  Sci.  Mo.,  April,  190 1. 


CHAPTER  V 

Lyonet:  The  Gentleman's  Magazine,  LIX,  1789;  the  famous  Traite 
Anatomique,  etc.,  1750,  1752,  not  rare.  Reaumur:  Portrait  and  life  in 
Les  Savants  Modernes,  p.  332.  Roesel:  Portrait  and  biography  in  Der 
monatlich  herausgegebenen  Insecten  Belustigung,  part  IV,  1761;  Zeigler  in 
Natur  und  Haus,  1904 — nine  figs.  Straus-Durckheim:  his  monograph 
on  Anatomy  of  the  Cockchafer,  rather  rare.  The  Minute  Anatomists; 
Straus-Durckheim,  Dufour,  Newport,  Leidig,  etc.,  in  Miall  and  Denney's 
The  Cockroach,  1886. 

Discovery  of  the  Protozoa:  Leeuwenhoek,  Miiller,  Ehrenberg, 
Dujardin,  etc.,  Kent's  Manual  of  the  Infusoria,  vol.  I.  Ehrenberg: 
Life  by  Laue,  1895. 


READING    LIST  46 1 


CHAPTER  VI 

ThePhysiologus:  Carus,  White  (for  titles  see  General  List).  Gesner: 
Brooks  in  Pop.  Sci.  Mo.,  1885 — illustrations;  Cuvier,  loc.  cit.;  Jardine's 
Naturalist's  Library,  vol.  VI;  Gesner' s  Historia  Animalium,  1551-1585. 
Aldrovandi:  Naturalist's  Library,  vol.  Ill;  Macgilivray, /oc.  ci/.  Jonston: 
Macgilivray.  Ray:  Macgilivray;  Nicholson;  Memorial  of,  in  the  Ray 
Society,  1846;  Correspondence  of,  Ray  Soc,  1848.  Linn^us  :  Mac- 
gilivray; Janus,  vol.  8,  1903;  Cuvier,  loc.  cit.;  Agassiz,  Essay  on  Classi- 
fication, 1859;  Jubilee  at  Upsala,  Science,  Apl.  26,  1907;  Caddy,  Through 
the  Fields  with  Linnaeus,  1887;  The  Systema  Naturae,  especially  the  tenth 
edition,  1758.  Leuckart:  Archives  de  Parasit.,  vol.  I,  no.  2;  Nature, 
1898.  General  Biological  Progress  from  Linn^us  to  Darwin: 
Geddes,  Proc.  Roy.  Soc.  Edinb.,  vol.  13,  1884-1886. 


CHAPTER  VII 

Camper:  Naturalist's  Library,  vol.  VII;  Vorlesungen,  by  his  son,  with 
short  sketch  of  his  life,  1793;  Cuvier,  loc.  cit.;  Kleinere  Schriften,  2  vols, 
with  copper  plates  illustrating  brain  and  ear  of  fishes,  etc.,  1 782-1 785. 
John  Hunter:  The  Scientific  Works  of,  2  vols.,  1861;  The  Asclepiad,  vol. 
VIII,  1 891;  the  same  article  with  illustrations  in  Richardson,  loc.  cit.;  Petti- 
grew,  loc.  cit.  ViCQ  d'Azyr:  Cuvier,  loc.  cit.;  Huxley  in  Life  of  Owen, 
p.  289;  His  works  in  6  vols.,  1805.  Cuvier:  Life  by  Flourens;  Memoirs  by 
Mrs.  Lee,  1833;  Buckle,  Hist.  Civ.,  vol.  I,  p.  633  et  seq.;  Lettres  de  Geo. 
Cuviera  C.  M.  PaiT,  1788-1792,  translated  from  the  German,  1858.  Cuvier's 
numerous  writings — The  Animal  Kingdom,  Lemons  d'Anat.  Comparee,  etc. 
— are  readily  accessible.  H.  Milne-Edwards  :  Biographical  sketch  in  A  nn. 
Kept.  Smithson.  Inst,  for  1893.  Lacaze-Duthiers:  Life  with  portraits 
in  Archives  de  Zool.  Experiment.,  vol.  10,  1902.  Richard  Owen:  Life  and 
Letters,  2  vols.,  1894;  Clark,  Old  Friends  at  Cambridge  and  Elsewhere, 
p.  349  et  seq.  J.  Fr.  Meckel:  Carus,  loc.  cit.  Gegenbaur:  Erlebtes  und 
Erstrebtes,  portrait,  1901;  Anat.  Anz.,  vol.  23,  1903;  Ann.  Rept.  Smithson. 
Inst.,  1904.  Cope:  Osborn  in  The  Century,  vol.  33,  1897;  Gill,  Edward 
Drinker  Cope,  Naturalist,  A  Chapter  in  the  History  of  Science,  Am.  Natur- 
alist, 1897;  Obituary  notice,  with  portraits,  Am.  Naturalist,  1897;  Pop. 
Sci.  Mo.,  vol.  19,  1881. 

CHAPTER   VIII 

Bichat:  Pettigrew;  Buckle,  Hist.  Civ.,  vol.  I,  p.  639;  The  Hundred 
Greatest  Men;  Les  Savants  Modernes,  p.  394;  TTie  Practitioner,  vol.  56, 
1896.     Koelliker:     His    Autobiography,    Erinnerungen     aus     Meinem 


462  READING   LIST 

Leben,  1899,  several  portraits,  interesting;  Weldon,  Life  and  Works  in 
Nature,  vol.  58,  with  fine  portrait;  Sterling,  Ann.  Rept.  Smithson.  Inst.,  1905^ 
Schultze:  Portrait  and  Necrology  by  Schwalbe  in  Archiv  jiir  Mikroscop^ 
Anat.,  vol,  10,  1874;  See  further  under  chapter  XII.  Virchow:  /.  Hop 
Univ.  Circulars,  vol.  XI,  189 1,  Celebration  of  Seventieth  Birthday  of  Virchow 
Addresses  by  Osier,  Welch,  and  others;  Jacobi,  Medical  Record,  N.  y! 
vol.  XX,  1881,  good;  Israel,  in  Ann.  Rept.  Smithson.  Inst.,  1902.  Leydig, 
Brief  sketch  in  his  Horae  Zoologicae,  1902.  Ramon  y  Cajal:  Portrait  in* 
Tenth  Anniversary  of  Clark  University,  1899. 


CHAPTER   IX 

The  best  brief  account  cf  the  Rise  of  Physiology  in  Verworn's  General 
Physiology,  1899.  More  recent  German  editions  of  the  same  work.  His- 
torical outline  in  Rutherford's  Text-Book  of  Physiology,  1880.  Galen's 
Physiology:  Verworn.  Harvey:  See  references  under  Chapter  III;  The 
analysis  of  his  writings  by  Willis  in  The  Works  of  Harvey,  translated  into 
English,  Sydenham  Soc,  1847;  See  also  Dr.  Moreton's  facsimile  repro- 
duction of  the  first  edition  (1628)  of  De  Motu  Cordis  et  Sanguinis,  1894. 
Haller:  Fine  portrait  in  his  Elementa  Physiologiae,  1758;  English  trans- 
lations of  the  Elementa.  Charles  Bell:  Pettigrew;  Good  summary  in 
Foster's  Life  of  Claude  Bernard,  p.  t,^  et  seq.  Johannes  Muller:  His 
life,  complete  list  of  works,  etc.,  in  Gedachtnissrede  auf  Johannes  Muller 
by  Du  Bois-Reymond,  i860;  Eloge  by  Vichow  in  Edinburgh  Med.  Journ., 
vol.  4;  Picture  of  his  monument  in  Coblenz,  Archiv  /.  Mik.  Anat.,  vol.  55; 
Brief e  von  J.  Muller  an  Andres  Retzius  (1830-185  7),  1900;  His  famous 
Handbuch  der  Physiologie  and  English  translations  should  be  inspected. 
Ludwig:  Burdon-Sanderson,  Ludwig  and  Modern  Physiology,  Sci.  Progress, 
vol.  V,  1896;  The  same  article  in  Ann.  Rept.  Smithson.  Inst.,  1896.  Claude 
Bernard:  Life  by  M.  Foster,  1899,  excellent. 


CHAPTER.  X 

Good  general  account  of  the  Rise  of  Embryology  in  Koelliker's  Embryolo- 
gie,  1880;  Minot,  Embryology  and  Medical  Progress,  Pop.  Sci.  Mo.,  vol.  69, 
1906;  Eycleshymer,  A  Sketch  of  the  Past  and  Future  of  Embryology, 
St.  Louis  Med.  Rev.,  1904.  Harvey:  As  fembryologist,  Brooks  in  /.  Hop. 
Univ.  Hospit.  Bull.,  vol.  VIII,  1897.  See  above.  Chaps.  Ill  and  IX 
for  further  references  to  Harvey.  Malpighi:  in  Embryology,  Locy  in 
Pop.  Sci.  Mo.,  1905 — portrait  and  selected  sketches  from  his  embryological 
treatises.  Wolff:  Wheeler,  Wolfif  and  the  Theoria  Generationis,  in 
Woods    Holl    Biological  Lectures,   1898;    Kirchoff  in  Jenaisclie  Zeitschr.y 


READING    LIST  463 

vol.  4,  1868;  Waldeyer,  Festrede  in  Sitzbr.  d.  K.  Preus.  Akad.  d.  Wissen- 
schaft.,  1904;  Haeckel  in  Evolution  of  Man,  vol.  I,  1892.  Bonnet  and 
Pre-delineation:  Whitman,  Bonnet's  Theory  of  Evolution,  also  Evolution 
and  Epigenesis,  both  in  Woods  HoU  Biological  Lectures,  1895.  VoN 
Baer:  Leben  und  Schriften,  his  autobiography  (1864),  2d  edition,  1886; 
Life  by  Steida,  1886;  Obituary,  Proc.  Roy.  Soc,  1878;  Waldeyer  in  Allg. 
Wien.  Med.  Ztg.,  1877;  Nature,  vol.  15;  Life  by  St5lzle,  1897;  Haeckel, 
loc.  cit.,  vol.  I;  Locy,  V.  Baer  and  the  Rise  of  Embryology,  Pop.  Sci.  Mo., 
1905;  Fine  portrait  as  young  man  in  Harper's  Mag.  for  1899;  Rev.  Scient., 
1879.  Kowalevsky:  Lankester  in  Nature,  vol.  66,  1902;  Portrait  and 
biog.  in  Ann.  Mus.  Hist.  Nat.  Marseille,  vol.  8,  1903.  Balfour:  M. 
Foster  in  Nature,  vol.  29,  1882;  Also  Life  with  portrait  in  the  Memorial 
Edition  of  Balfour's  Works;  Waldeyer  in  Arch.  f.  Mik.  Anat.,  vol.  21,  1882; 
Osborn  Recollections,  with  portrait.  Science,  vol.  2,  1883.  His:  Mall  in 
Am.  Journ.  Anat.,  vol.  4,  1905;  Biography  in  Anat.  Anz.,  vol.  26,  1904. 


CHAPTER   XI 

The  Cell-Doctrine  by  Tyson,  1878.  The  Cell-Theory,  Huxley,  Medico- 
chir.  Review,  1853,  also  in  Scientific  Memoirs,  vol.  I,  1898;  The  Modern 
Cell-Theory,  M'Kendrick,  Proc.  Phil.  Soc.  Glasgow,  vol.  XIX,  1887;  The 
Cell-Theory,  Past  and  Present,  Turner,  Nature,  vol.  43,  1890;  The  Cell- 
Doctrine,  Burnett,  Trans.  Am.  Med.  Assn.,  vol.  VI,  1853;  First  illustration 
of  cells  in  Rob't  Hooke's  Micrographia,  1665,  1780,  etc.;  The  Cell  in  De- 
velopment and  Inheritance,  Wilson,  1896;  Article  Cell,  in  Chambers's  (New) 
Cyclopaedia,  by  Thomson.  Schleiden:  Sketch  of,  Pop.  Sci.  Mo.,  vol. 
22,  1882-1883;  Sachs'  Hist,  of  Botany  1890;  Translation  of  his  original 
paper  of  1838  (Ueber  Phytogenesis) — illustrations — Sydenham  Soc,  1874. 
Schwann:  Life,  Pop.  Sci.  Mo.,\o\.  37,  1900;  Sa  Vie  et  Ses  Travaux, 
Fredericq,  1884;  Nachruf,  Henle,  Archiv  f.  Mik.  Anat.,  vol.  21,  1882; 
Lankester,  Nature,  vol.  XXV,  1882;  The  Practitioner,  vol.  49,  1897;  The 
Catholic  World,  vol.  71,  1900.  Translation  of  his  contribution  of  1839 
(Mikroscopische  Untersuchungen  ueber  die  Uebereinstimmung  in  der  Struc- 
tur  und  dem  Wachstum  der  Thiere  und  Pflanzen),  Sydenham  Soc,  1847. 


CHAPTER   XII 

On  the  Physical  Basis  of  Life,  Huxley,  1868;  Reprint  in  Methods  and 
Results,  1894.  Article  Protoplasm  in  Ency.  Brit,  by  Geddes.  Dujardin: 
Notice  Biographique,  with  portraits  and  other  illustrations,  Joubin,  Archives 
de  Parasitol.,  vol.  4,  1901;  portrait  of  Dujardin  hitherto  unpublished.  Du- 
jardin's  original  description  of    Sarcode,  Ann.  des  Sci.  Nat.  {Botanique^, 


464  READING    LIST 

vol.  4,  p.  367,  1835.  Von  Mohl:  Sachs'  History  of  Botany,  1890.  Trans- 
lation of  his  researches,  Sydenham  Soc,  1847.  Cohn:  Blatter  der  Er- 
innerung,  1898,  with  portrait.  Schultze:  Necrology,  by  Schwalbe  in 
Archiv  /.  Mik.  Anat.,  vol.  10,  1874,  with  portrait.  Schultze's  paper  found- 
ing the  protoplasm  doctrine  in  Archiv  j.  Anat.  und  Phys.,  1861,  entitled 
Ueber  Muskelkorperchen  und  das  was  man  eine  Zelle  zu  nennen  habe. 


CHAPTER  XIII 

Spontaneous  Geneziation:  Tyndall,  Pop.  Set.  Mo.,  vol.  12,  1878; 
Also  in  Floating  Matter  of  the  Air,  1881 ;  J.  C.  Dalton  in  iV.  F.  Med.  Journ.y 
1872;  Dunster,  good  account  in  Proc.  Ann  Arbor  Sci.  Assn.,  1876;  Hux- 
ley, Kept.  Brit.  Assn.  for  Adv.  Sci.,  1870,  republished  in  many  journals, 
reprint  in  Scientif.  Memoirs,  vol.  IV,  1901.  Redi:  Works  in  9  vols.,  1809- 
181 1,  with  life  and  letters  and  portraits;  Good  biographical  sketch  in 
Archives  de  Parasitol.,  vol.  I,  1898;  Redi's  Esperienze  Intorno  Alia  Genera- 
zione  DeglTnsetti,  2  plates,  first  edition,  1668,  in  Florence,  40;  reprinted 
at  various  dates,  not  uncommon;  English  translation  by  Mab.  Bigelow, 
1909.  Spallanzani:  Foster,  Lects.  on  Physiol.;  Huxley,  loc.  cit.;  Dunster, 
loc.  cit.;  L'Abbato  Spallanzani,  by  Pavesi,  1901,  portrait.  Pouchet:  His 
treatise  of  historical  importance — Heterogenic,  ou  Traite  de  la  Generation 
Spontanee,  base  sur  des  Nouvelles  Experiences,  1859.  Pasteur:  Life  by 
Rene  Vallery-Radot,  2  vols.,  1902;  Percy  and  G.  Frankland,  1901;  Pasteur 
at  Home,  illustrated,  Tarbell  in  McClure's  Mag.,  vol.  1, 1893;  Also  McClure's, 
vol.  19,  1902,  review  of  Vallery-Radot's  Life  of  Pasteur;  Nature,  vol.  52, 
1895;  Les  Savants  Modernes,  p.  316;  Life  by  his  son-in-law,  translated  by 
Lady  Hamilton,  1886;  Sketches  of  Pasteur,  very  numerous.  Bacteriology: 
Woodhead,  Bacteria  and  their  Products,  1891;  Fraenkel,  Text-Book  of 
Bacteriology,  1891;  Prudden,  The  Story  of  Bacteria,  etc.,  1891.  Germ- 
Theory  OF  Disease:  Crookshank's  Bacteriology,  3d  edition,  1890.  Koch: 
Pop.  Sci.  Mo.,  vol.  s6y  1889;  Review  of  Reviews,  vol.  2,  1890;  Sketches  and 
references  to  his  discoveries  numerous.  Lister:  Pop.  Sci.  Mo.,  vol.  52, 
1898;  Review  of  Reviews,  vol.  14,  1896;  celebration  of  Lister's  80th  birthday, 
Pop.  Sci.  Mo.,  June,  1907;  Janus,  vol.  5,  1900.  The  New  Microbe  Inocula- 
tion of  Wright,  Harper's  Mag.,  July,  1907. 

CHAPTER  XIV 

The  History  and  Theory  of  Heredity,  J.  A.  Thomson,  Proc.  Roy.  Soc. 
Edinb.,  vol.  XVI,  1889;  Chapter  on  Heredity  in  Thomson's  Science  of  Life, 
1899;  3^1so  in  his  Study  of  Animal  Life,  1892;  Heredity  and  Environment  in 
the  Development  of  Men,  Conklin,  1915.  Mendel:  Mendel's  Principles 
of  Heredity,  with  translations  of  his  original  papers  on  hybridization,  Bate- 


READING  LIST  465 

son,  1902;  Mendel's  Versuche  iiber  Pflanzenhybriden,  two  papers  (1865  and 
1869),  edited  by  Tschermak,  1901;  Ann.  Rept.  SmUhson.  Inst.,  1901-1902; 
Pop.  Sci.  Mo.,  vol.  62,  1903;  vol.  63,  1904;  Science,  vol.  23,  1903.  Galton: 
Pop.  Sci.  Mo.,  vol.  29,  1886;  Nature,  vol.  70,  1907;  Memories  of  my  Life, 
1908;  Galton's  Natural  Inheritance,  1889.  Weismann:  Brief  Autobiography, 
with  portrait,  in  The  Lamp,  vol.  26,  1903;  Solomonsen,  Bericht  iiber  die 
Feier  des  70  Geburtstages  von  August  Weismann,  1904;  Weismann's  The 
Germ-Plasm,  1893,  and  The  Evolution  Theory,  1904. 

CHAPTER   XV 

History  of  Geology  and  Paleontology,  Zittel,  1901.  The  Founders  of 
Geology,  Geikie,  2d  edition,  1905.  History  and  Methods  of  Paleonto- 
logical  Discovery,  Marsh,  Proceed.  Am.  Adv.  Sci.,  1879.  Same  article  in 
Pop.  Sci.  Mo.,  vol.  16,  1879-1880.  The  Rise  and  Progress  of  Paleontology, 
Huxley,  Pop.  Sci.  Mo.,  vol.  20,  1882.  Lyell:  Charles  Lyell  and  Modern 
Geology,  Bonney,  1895;  Sketch  in  Pop.  Sci.  Mo.,  vol.  I,  1872,  also  vol. 
20,  1881-1882.  Owen:  Life  of,  by  his  grandson,  2  vols.,  1894;  See  also 
above  under  Chapter  VIL  Agassiz:  Life  and  Correspondence,  by  his 
wife,  2  vols.,  1885;  Life,  letters  and  works,  Marcou,  2  vols.,  1896;  What 
we  Owe  to  Agassiz,  Wilder,  Pop.  Sci.  Mo.,  July,  1907;  Agassiz  at  Penikese, 
Am.  Nat.,  1898.  Cope:  A  Great  NaturaHst,  Osborn  in  The  Century,  1897; 
See  above,  under  Chapter  VII,  for  further  references.  Marsh:  Pop,  Sci.  Mo., 
rol.  13,  1878;  Sketches  of.  Nature,  \o\.  59,  1898-99;  Science,  vol.  9,  1899; 
Am.  J.  Sci.,  vol.  157,  1899.  Zittel:  Biographical  Sketch  with  portrait, 
Schuchert,  Ann.  Rept.  Smithson.  Inst.,  1903-1904.  Osborn,  Papers  on 
Paleontological  Discovery  in  Science  from  1899  onward;  The  Age  of  Mam- 
mals, 1910.  The  Faylim  Expedition  of  the  Am.  Museum  of  Nat,  History, 
Science,  March  29,  1907. 

Note.  Since  the  four  succeeding  chapters  deal  with  the  Evolution 
Theory,  it  may  be  worth  while  to  make  a  few  general  comments  on  the  liter- 
ature pertaining  to  Organic  Evolution.  The  number  of  books  and  articles 
is  very  extensive,  and  I  have  undertaken  to  sift  from  the  great  number  a 
limited  list  of  the  more  meritorious.  Owing  to  the  prevalent  vagueness 
regarding  evolution  theories,  one  is  likely  to  read  only  about  Darwin  and 
Darwinism.  This  should  be  avoided  by  reading  as  a  minimum  some  good 
reference  on  Lamarck,  Weismann,  and  De  Vries,  as  well  as  on  Darwin. 
It  is  well  enough  to  begin  with  Darwin's  Theory,  but  it  is  not  best  to  take 
his  Origin  of  Species  as  the  first  book.  To  do  this  is  to  place  oneself  fifty 
years  in  the  past.  The  evidences  of  Organic  Evolution  have  greatly  multi- 
plied since  1859,  and  a  better  conception  of  Darwin's  Theory  can  be  ob- 
tained by  reading  first  Romanes's  Darwin  and  After  Darwin,  vol.  L  This  to 
be  followed  by  Wallace's  Darwinism,  and,  thereafter,  the  Origin  of  Species 


466  READING  LIST 

may  be  taken  up.  These  will  give  a  good  conception  of  Darwin's  Theory, 
and  they  should  be  followed  by  reading  in  the  order  named:  Packard's 
Lamarck;  Weismann's  The  Evolution  Theory;  and  De  Vries's  The  Origin 
of  Species  and  Varieties  by  Mutation.  Simultaneously  one  may  read  with 
great  profit  Osbom's  From  the  Greeks  to  Darwin,  and  Kellogg's  Darwinism 
To-Day,  1907. 

CHAPTER  XVI 

General:  Romanes,  Darwin  and  After  Darwin,  1892,  vol.  I,  chaps. 
I-V;  Same  author.  The  Scientific  Evidences  of  Organic  Evolution;  Weis- 
mann  Introduction  to  the  Evolution  Theory,  1904;  Osborn,  Alte  und  Neue 
Probleme  der  Phylogenese,  Ergehnisse  der  Anat.  u.  Entwickel.,  vol.  Ill,  1893; 
Ziegler,  Ueber  den  derzeitigen  Stand  der  Descendenzlehre  in  der  Zoologie, 
1902;  Jordan  and  Kellogg,  Evolution  and  Animal  Life,  1907,  chaps.  I  and 
XIV.  Evolutionary  Series — Shells:  Romances,  loc.  cit.;  Hyatt,  Trans- 
formations of  Planorbis  at  Steinheim,  Proc.  Am.  Ass.  Adv.  Sci.,  vol.  29,  1880. 
Horse:  Lucas,  The  Ancestry  of  the  Horse,  McClure's  Mag.,  Oct.,  1900; 
Huxley,  Three  Lectures  on  Evolution,  in  Amer.  Addresses.  Embryology — 
Recapitulation  Theory:  Marshall,  Biolog.  Lectures  and  Addresses, 
1897;  Vertebrate  Embryology,  1892;  Haeckel,  Evolution  of  Man,  1892. 
Primitive  Man:  Osborn,  Discovery  of  a  Supposed  Primitive  Race  of 
Men  in  Nebraska,  Century  Mag.,  Jan.,  1907;  Haeckel,  The  Last  Link, 
1898.  Huxley,  Man's  Place  in  Nature,  collected  essays,  1900;  published 
in  many  forms.     Romanes,  Mental  Evolution  in  Man  and  Animals. 


CHAPTER   XVII 

Lamarck:  Packard,  Lamarck,  the  Founder  of  Evolution,  His  Life 
and  Work,  with  Translations  of  his  Writings  on  Organic  Evolution,  1901; 
Lamarck's  Philosophic  Zoologique,  1809.  Recherches  sur  I'Organisation 
des  corps  vivans,  1802,  contains  an  early,  not  however  the  first  statement  of 
Lamarck's  views.  For  the  first  published  account  of  Lamarck's  theory 
see  the  introduction  to  his  Systeme  des  Animaux  sans  Vertebres,  1801. 
Neo-Lamarckism:  Packard,  loc.  cit.;  also  in  the  Introduction  to  the 
Standard  Natural  History,  1885;  Spencer,  The  Principles  of  Biology,  1866 
— based  on  the  Lamarckian  principle.  Cope,  The  Origin  of  Genera,  1866 
Origin  of  the  Fittest,  1887;  Primary  Factors  of  Organic  Evolution,  1896, 
the  latter  a  very  notable  book.  Hyatt,  Jurassic  Ammonites,  Proced.  Bost 
Sci.  Nat.  Hist.,  1874.  Osborn,  Trans.  Am.  Phil.  Soc,  vol.  16,  1890.  Eigen 
mann.  The  Eyes  of  the  Blind  Vertebrates  of  North  America,  Archiv  f. 
Entwickelungsmechanik,  vol.  8,  1899. 

Darwin's  Theory  (For  biographical  references  to  Darwin  see  below 


READING   LIST  467 

under  Chapter  XIX):  Wallace,  Darwinism,  1889;  Romanes,  Darwin 
and  After  Darwin,  vol.  I,  1892;  Metcalf,  An  Outline  of  the  Theory  of 
Organic  Evolution,  1904,  good  for  illustrations.  Color;  Poulton,  The 
Colors  of  Animals;  Chapters  in  Weismann's  The  Evolution  Theory,  1904. 
Mimicry;  Weismann,  loc.  cit.  Sexual  Selection:  Darwin,  The  Descent 
of  Man,  new  ed.,  1892.  Inadequacy  or  Nat.  Selection:  Spencer,  The 
Inadequacy  of  Natural  Selection,  1893;  Morgan,  Evolution  and  Adapta- 
tion, 1903.  Kellogg,  Darwinism  To-day,  1907,  contains  a  good  account 
of  criticisms  against  Darwinism. 


CHAPTER   XVIII 

Weismann's  The  Evolution  Theory,  translated  by  J.  A.  and  Margaret 
Thomson,  2  vols.,  1904,  contains  the  best  statement  of  Weismann's  views. 
It  is  remarkably  clear  in  its  exposition  of  a  complicated  theory.  The 
Germ-Plasm,  1893;  Romanes's  An  Examination  of  Weismannism,  1893. 
Inheritance  of  Acquired  Characters:  Weismann's  discussion,  loc.  cit., 
vol.  II,  very  good.  Romanes's  Darwin  and  After  Darwin,  vol.  II.  Per- 
sonality OF  Weismann:  Sketch  and  brief  autobiography,  in  The  Lamp. 
vol.  26,  1903,  portrait;  Solomonsen,  Berichtiiber  die  Feier  des  70  Geburts- 
tages  von  August  Weismann,  1905,  2  portraits. 

Mutation-Theory  of  De  Vries:  Die  Mutations-Theorie,  looi; 
Species  and  Varieties,  their  Origin  by  Mutation,  1905;  Morgan,  Evolution 
and  Adaptation,  1903,  gives  a  good  statement  of  the  Mutation  Theory, 
which  is  favored  by  the  author;  Whitman,  The  Problem  of  the  Origin  of 
Species,  Congress  of  Arts  and  Science,  Universal  Exposition,  St.  Louis,  1904; 
Davenport,  Evolution  without  Mutation,  Journ.  Exp.  ZooL,  April,  1905. 


CHAPTER  XIX 

For  early  phases  of  Evolutionary  thought  consult  Osborn,  From  the 
Greeks  to  Darwin,  1894,  and  Clodd,  Pioneers  of  Evolution,  1897.  Suarez 
and  the  Doctrine  of  Special  Creation:  Huxley,  in  Mr.  Darwin's 
Critics,  Cont.  Rev.,  p.  187,  reprinted  in  Critiques  and  Addresses,  1873. 
Buffon:  In  Packard's  Life  of  Lamarck,  chapter  13.  E.  Darwin: 
Krause's  Life  of  E.  Darwin  translated  into  English,  1879;  Packard,  loc. 
cit.  Goethe:  Die  Idee  der  Pflanzenmetamorphose  bei  Wolff  und  bei 
Goethe,  Kirchoff,  1867;  Goethe's  Die  Metamorphose  der  Pflanzen,  1790. 
Oken:  His  Elements  of  Physiophilosophy,  Ray  Soc,  1847.  Cuvier  and 
St.  Hilaire:  Perrier,  La  Philosophie  Zoologique  avant  Darwin,  1884; 
Osborn,  loc.  cit.  Darwin  and  Wallace:  The  original  communications  of 
Darwin  and  Wallace,  with  a  letter  of  transmissal  signed  by  Hooker  and  Lyell, 


468  READING  LIST 

published  in  the  Trans.  LinncBan  Soc.  for  1858,  were  reprinted  in  the  Pop. 
Set.  Mo.,  vol.  60,  igoi;  Judd,  The  Coming  of  Evolution,  1910.  Darwin: 
Personality  and  biography  (For  references  to  his  theory  see  under  Chapter 
XVII);  Life  and  letters  by  his  son,  3  vols.,  1887,  new  ed.,  1896;  More  Letters 
of  Charles  Darwin,  2  vols.,  1903;  Chapter  in  Marshall's  Lectures  on  the  Dar- 
winian Theory;  Darwin,  Naturalist's  Voyage  around  the  World,  1880; 
Gould,  Biographical  Clinics,  for  Darwin's  illness  due  to  eye-strain;  Poulton, 
Chas.  Darwin,  and  the  Theory  of  Natural  Selection,  1896.  Wallace:  My 
Life,  2  vols.,  1905;  The  Critic,  Oct.,  1905.  Huxley:  Life  and  Letters  by  his 
Son,  1901;  Numerous  sketches  at  the  time  of  his  death,  1895;  in  Nature, 
Nineteenth  Century,  Pop.  Sci.  Mo.,  etc.,  etc.  Haeckel.  His  Life  and  Work 
by  Bolsche,  1906. 

CHAPTER   XX 

It  is  deemed  best  to  omit  the  references  to  Technical  papers  upon  which 
the  summaries  of  recent  tendencies  are  based.  Morgan's  Experimental 
Zoology,  1907.  Jennings,  Behavior  of  the  Lower  Organisms,  1906.  Mos- 
quitoes and  other  insects  in  connection  with  the  transmission  of  disease, 
see  Folsom,  Entomology,  1906,  chapter  IX,  p.  299.  Biological  Lab- 
oratories: Dean,  The  Marine  Biological  Stations  of  Europe,  Ann.  Rept. 
Smithson.  Inst.,  1894;  Marine  Biolog.  Station  at  Naples,  Harper's  Mag., 
1901;  The  Century,  vol,  10  (Emily  Nunn  Whitman);  WilHams,  A 
History  of  Science,  vol.  V,  chapter  V,  1904;  Am.  Nat.,  vol.  31,  1897; 
Pop.  Sci.  Mo.,  vol.  54,  1899;  ihid.,  vol.  59,  1901.  Woods  HoU  Station — A 
Marine  University,  Ann.  Rept.  Smithson.  Inst.,  1902. 


INDEX 


INDEX 


Abiogenesis,  277 

Acquired  characters,  inheritance  of, 
315;  Weismann  on,  404 

Agassiz,  essay  on  classification,  137; 
agreement  of  embryological  stages 
and  the  fossil  record,  336;  fossil 
fishes,  336;  portrait,  336 

Aldrovandi,  115 

Alternative  inheritance,  317 

Amphimixis,  the  source  of  varia- 
tions, 402 

Anatomical  sketches,  the  earliest, 
32;  from  Vesa'ius,  31,  33 

Anatomical  studies,  recent  tenden- 
cies of,  450 

Anatomy,  of  Aristotle,  23;  begin- 
nings of,  23;  earliest  known  illus- 
trations, 32;  of  Galen,  24;  of  the 
Middle  Ages,  24;  comparative, 
rise  of,  141- 165;  of  insects, 
Dufour,  log;  Lyonet,  91;  Mal- 
pighi,  63;  Newport,  100;  Reau- 
mur, 96;  Roesel,  96;  Straus- 
Diirckheim,  96;  Swammerdam, 
70,  73-77;  minute,  progress  of, 
89-104;  of  plants.  Grew,  56; 
Malpighi,  66 

Ancients,  return  to  the  science  of, 
112 

Animal  behavior,  studies  of,  451 

Animal  kingdom  of  Cuvier,  133 

Aquinas,  St.  Thomas,  on  creation, 

417 
Arcana   Naturae,   of   Leeuwenhoek, 

78 
Aristotle,  9-15;  books  of,  13;  errors 
of,  13;  estimate  of,  10;  extensive 
knowledge    of    animals,    12;    the 
founder  of  natural  history,  9;  in- 
fluence of,   15;  personal  appear- 
ance,  13,   14;  portrait,   14;  posi- 
tion in  the  development  of  science, 
II 
Arrest  of  inquiry,  efifect  of,  1 7 
Augustine,  St.,  on  creation,  417 
Authority   declared   the   source   of 
knowledge,  18 


B 

Bacteria,  discovery  of,  276;  disease- 
producing,  300;  and  antiseptic 
surgery,  303;  nitrifying,  of  the 
soil,  305 

Bacteriology,  development  of,  276 

Baer,  Von,  and  the  rise  of  embryol- 
ogy, 195-236;  his  great  classic  on 
development  of  animals,  214;  and 
germ-layers,  218;  makes  embryol- 
ogy comparative,  220;  and  Pan- 
der, 218;  period  in  embryology, 
214-226;  portraits,  216,  217;  his 
rank  in  embryology,  220;  his  es- 
pecial service,  217;  sketches  from 
his  embryological  treatise,  221 

Balfour,  masterly  work  of,  226;  his 
period  in  embryology,  226-232; 
personality,  228;  portrait,  227; 
tragic  fate,  228;  university  career, 
227 

Bary,  H.  A.  de,  271;  portrait,  272 

Bassi,  and  the  germ-theory  of  dis- 
ease, 294 

Bell,  Charles,  discoveries  on  the  ner- 
vous system,  183;  portrait,  184 

Berengarius,  26 

Bernard,  Claude,  in  physiology,  190; 
personality,  191;  portrait,  191 

Biblia  Naturae  of  Swammerdam,  73 

Bichat,  and  the  birth  of  histology, 
166-178;  Buckle's  estimate  of, 
166,  167;  education,  167;  in 
Paris,  167;  personality,  168;  phe- 
nomenal industry,  168;  portrait, 
169;  results  of  his  work,  170; 
writings,  170;  successes  of,  170 

Binomial  nomenclature  of  Linnaeus, 
126 

Biological  facts,  application  of,  451 

Biological  laboratories,  establish- 
ment and  maintenance  of,  452; 
the  station  at  Naples,  452;  picture 
of,  453;  the  Woods  HoU  station, 
452 

Biological  periodicals,  454 

Biological  progress,  continuity  of, 
442;  atmosphere  engendered  by. 


471 


472 


INDEX 


456;  from  Linnaeus  to  Darwin, 
138-140  . 

Biology,  defined,  4;  domain  of,  4,  5; 
epochs  of,  20;  progress  of,  3,  5; 
applied,  451 

Boerhaave,  quoted,  71,  72;  and 
Linnaeus,  122 

Bois-Reymond  Du,  189;  portrait, 
189 

Bones,  fossil,  324,  326 

Bonnet,  and  emboitcment,  208;  op- 
position to  Wolff,  211;  portrait, 
212 

Books,  the  notable,  of  biology,  443 

Brown,  Robert,  discovers  the  nu- 
cleus in  plant'cells,  243 

Buckland,  326 

Buckle,  on  Bichat,  166,  167 

Buffon,  129,  419;  portrait,  420;  po- 
sition in  evolution,  420 


Caesalpinus,  on  the  circulation,  50 

Cajal,  Ramon  y,  176;  portrait,  176 

Calkins,  on  protozoa,  109 

Camper,  anatomical  work  of,  143; 
portrait,  144 

Carpenter,  quoted,  170 

Carpi,  the  anatomist,  26 

Castle,  experiments  on  inheritance, 
318 

Catastrophism,  theory  of,  Cuvier, 
328;  Lyell  on,  si3 

Cell,  definition  of,  258;  diagram  of, 
257;  earliest  known  pictures  of, 
238,  239;  in  heredity,  257 

Cell-lineage,  234,  450 

Cell-theory,  announcement  of,  242; 
effect  on  embryology,  222,  224; 
founded  by  Schleiden  and 
Schwann,  242;  Schleiden's  con- 
tribution, 247;  Schwann's  trea- 
tise, 248;  modifications  of,  250; 
\  ague  foreshadowings  of,  237 

Child,  studies  on  regulation,  448 

Chromosomes,  254,  313 

Circulation  of  the  blood,  Harvey, 
46,  47;  Servetus,  50;  Columbus, 
50;  Caesalpinus,  50;  in  the  capil- 
laries, 84;  Leeuwenhoek's  sketch 
of,  83;  Vesalius  on,  with  illustra- 
tion, 49 

Classification  of  animals,  tabular 
view  of,  T37-138 

Cohn,  portrait,  271 


Color,  in  evolution,  392 

Columbus,  on  the  circulation,  50 

Comparative  anatomy,  rise  of,  141- 
165;   becomes  experimental,    165 

Cope,  in  comparative  anatomy,  165; 
portrait,  338;  important  work  in 
palaeontology,  339,  441 

Creation,  Aquinas  on,  417;  St. 
Augustine  on,  416;  special,  418; 
evolution  the  method  of,  350 

Cuvier,  birth  and  early  education, 
149;  and  catastrophism,  328; 
comprehensiveness  of  mind,  154; 
correlation  of  parts,  133;  debate 
with  St.  Hilaire,  424;  domestic 
life,  155;  forerunners  of,  143; 
founds  comparative  anatomy,  154; 
founder  of  vertebrate  pahuontol- 
ogy,  327;  his  four  branches  of  the 
animal  kingdom,  132;  goes  to 
Paris,  151;  life  at  the  seashore, 
150;  opposition  to  Lamarck,  422; 
portraits,  152,  153;  physiognomy, 
152;  and  the  rise  of  comparative 
anatomy,  141-156;  shortcomings 
of,  156;  successors  of,  156;  type- 
theory  of,  133 


Darwin,  Charles,  his  account  of  the 
way  his  theory  arose,  435;  factors 
of  evolution,  386;  habits  of  work, 
432;  home  life,  431;  at  Down, 
434;  ill  health,  434;  naturalist  on 
the  Beagle,  433;  natural  selection, 
389;  opens  note-book  on  the  origin 
of  species,  434;  personality,  430; 
portraits,  387,  431;  parallelism  in 
thought  with  Wallace,  435;  pub- 
lication of  the  Origin  of  Species^ 
437;  his  other  works,  397,  437; 
theory  of  pangenesis,  307;  varia- 
tion in  nature,  388;  the  original 
drafts  of  his  theory  sent  by 
Hooker  and  Lyell  to  the  Linnaean 
Society,  428-430;  working  hours, 
434;  summary  of  his  theory,  411 

Darwin,  Erasmus,  421;  portrait, 
421 

Darwinism  and  Lamarckism  con- 
fused, 397;  not  the  same  as  or- 
ganic evolution,  349 

Davenport,  experiments,  321 

Deluge,  and  the  deposit  of  fosals, 
32s 


INDEX 


473 


De  Varies,  mutation  theory  of,  408; 

portrait,  409;  summary,  411 
Dufour,  Leon,  on  insect  anatomy,  100 
Dujardin,   250,   262;  discovers  sar- 

code,    250,    266;    portrait,    265; 

writings,  264 


Edwards,  H.  Milne-,  157;  portrait, 

157 

Ehrenberg,  106,  107;  portrait,  108 

Eimer,  413 

Embryological  record,  interpreta- 
tion of,  229 

Embryology,  Von  Baer  and  the  rise 
of,  194-236;  experimental,  232; 
gill-clefts  and  other  rudimentary 
organs  in  embryos,  363;  theoret- 
ical, 235 

Epochs  in  biological  history,  20 

Evolution,  doctrine  of,  generalities 
regarding,  347;  controversies  re- 
garding the  factors,  348,  375;  fac- 
tors of,  374;  effect  on  embryology, 
225;  on  palaeontology,  334;  na- 
ture of  the  question  regardmg, 
350;  a  historical  question,  350; 
the  historical  method  in,  350; 
sweep  of,  372;  one  of  the  greatest 
acquisitions  of  human  knowledge, 
372;  predictions  verified,  373; 
theories  of,  375;  Lamarck,  375; 
Darwin,  392;  Weismann,  398; 
De  Vries,  408;  order  of  the  best 
reading,  465;  summary  of  evo- 
lution theories,  410;  vagueness 
regarding,  348 

Evolutionary  series,  353;  shells,  353; 
horses,  356 

Evolutionary  thought,  rise  of,  415- 
441 ;  views  of  certain  fathers  of  the 
church,  416 

Experimental  observation,  intro- 
duced by  Harvey,  39-53 

Experimental  work  in  biology,  447 


Fabrica,  of  Vesalius,  32 

Fabricius,    Harvey's    teacher,    41; 

portrait,  43 
Factors  of  evolution,  375 
Fallopius,  37;  portrait,  37 
Flood,  fossils  ascribed  to,  325 
Fossil  remains,  the  science  of,  322- 

343;  bones,  324,  327;  horses  in 


America,  357;  collections  in  New 
Haven,  357;  in  New  York,  357; 
man,  342,  366;  Neanderthal  skull, 
368;  ape-like  man,  369;  remains 
of  man:  Neanderthal,  368;  Java, 
369;  Heidelberg,  369;  Piltdown, 
370 

Fossil  remains  an  index  to  past  his- 
tory, 331 

Fossils,  arrangement  in  strata,  330; 
ascribed  to  the  flood,  325;  their 
comparison  with  living  animals, 
326;  from  the  Fayum  district,  343; 
method  of  collecting,  342;  nature 
of,  324;  determination  of,  by 
Cuvier,  327;  Da  Vinci,  324; 
Steno,  324;  strange  views  re- 
garding, 322 


Galen,  23,  180;  portrait,  25 

Gal  ton,  law  of  ancestral  inheritance, 
321;  portrait,  320 

Geer,  De,  on  insects,  95 

Gegenbaur,  163;  portrait,  164 

Generation,  Wolff's  theory  of,  210 

Germ-cells,  organization  of,  210 

Germ-layers,  218 

Germ-plasm,  continuity  of,  399; 
complexity  of,  401 ;  the  hereditary 
substance,  321;  union  of  germ- 
plasms  the  source  of  variations,  402 

Germ-theory  of  disease,  293 

Germinal  continuity,  224,  309;  doc- 
trine of,  224,  312,  399 

Germinal  elements,  306 

Germinal  selection,  403 

Germinal  substance,  311 

Gesner,  112;  personality,  113;  por- 
trait, 114;  natural  history  of,  113 

Gill-clefts  in  embryos,  363 

Goodsir,  174 

Grew,  work  of,  56 


Haeckel,  439;  portrait,  440 

Haller,  fiber-theory,  242;  opposition 
to  Wolff,  211;  in  physiology,  181; 
portrait,  182 

Harvey,  and  experimental  observa- 
tion, 39-53;  his  argument  for  the 
circulation,  51;  discovery  of  the 
circulation,  47;  his  great  classic, 
46;  education,  40;  in  embryology, 
198;  embryological  treatise,  199, 


474 


INDEX 


200;  frontispiece  from  his  genera- 
tion of  animals  (1651),  201;  in- 
fluence of,  52;  introduces  exper- 
imental method,  47;  at  t*adua,  41; 
period  in  physiology,  180;  per- 
sonal appearance  and  qualities, 
42,  44,  45;  portrait,  44;  prede- 
cessors of,  48;  question  as  to  his 
originaMty,  46;  his  teacher,  43; 
writings,  45 

Heredity,  306;  a  cellular  study,  257; 
according  to  Darwin,  308;  Weis- 
mann,  310;  application  of  statis- 
tics to,  315;  inheritance  of  ac- 
quired characters,  315;  steps  in 
advance  of  knowledge  of,  309 

Hertwig,  Oskar,  portrait,  231;  ser- 
vice in  embryology,  2^2;  Rich- 
ard, quoted,  125 

Hilaire,  St.,  portrait,  424;  see  St. 
Hilairc 

His,  Wilhelm,  232;  portrait,  233 

Histology,  birth  of,  166-178;  Bichat 
its  founder,  170;  normal  and 
pathological,  172;  text-books  of, 
177    ^ 

Hookc,  Robert,  55;  his  microscope 
illustrated,  55 

Hooker,  letter  on  the  work  of  Dar- 
win and  Wallace,  428-430 

Horse,  evolution  of,  356 

Human  ancestry,  links  in,  366-372 

Human  body,  evolution  of,  365 

Human  fossils,  342,  367 

Hunter,  John,  144;  portrait,  145 

Huxley,  in  comparative  anatomy, 
161;  influence  on  biology,  438;  in 
palaeontology,  337;  portrait,  438 


Inheritance,  alternative,  Mendel, 
317;  ancestral,  321;  Darwin's 
theory  of,  307;  material  basis  of, 
312-314;  nature  of,  306 

Inheritance  of  acquired  characters, 
315;  Lamarck  on,  383;  Weis- 
mann  on,  404 

Inquiry,  the  arrest  of,  17 

Insects,  anatomy  of,  Dufour,  106; 
Malpighi,  63;  illustration,  65; 
Newport,  100;  Leydig,  102; 
Straus-Diirckheim,  96;  Swammer- 
dam,  70,  75;  illustration,  76;  theol- 
ogy of,  91 

Isolation,  413 


Jardin  du  Roi  changed  to  Jardin  des 

Plantes,  378 
Jennings,  on  animal  behavior,  109, 

441 
Jonston,  114 

K 

Klein,  118 

Koch,  Robert,  discoveries  of,  300; 

portrait,  301 
Koelliker,   in  embryology,    224;   in 

histology,  171;  portrait,  173 
Kowalevsky,    in    embryology,    224; 

portrait,  225 

L 

Lacaze-Duthiers,  158;  portrait,  159 
Lamarck,  changes  from  botany  to 
zoology,  378;  compared  with 
Cuvier,  329;  education,  377;  first 
announcement  of  his  evolutionary 
views,  381;  forerunners  of,  419; 
first  use  of  a  genealogical  tree,  131; 
founds  invertebrate  pala;ontology, 
328;  on  heredity,  ^8^^;  laws  of 
evolution,  382;  military  exi)cri- 
ence,  376;  opposition  to,  422; 
Philosophic  Zoologique,  381;  por- 
trait, 373;  position  in  science,  132; 
salient  points  in  his  theory,  384; 
his  theory  of  evolution,  380;  com- 
pared with  that  of  Darwin,  396, 
397;  time  and  favorable  condi- 
tions, 384;  use  and  disuse,  380 
Lecuwenhoek,  77-87;  new  bio- 
graphical facts,  78;  capillary 
circulation,  84,  85,  sketch  of,  83; 
comparison  with  Malpighi  and 
Swammerdam,  87;  discovery  of 
the  protozoa,  105;  other  discov- 
eries, 85;  and  histology,  178;  his 
microscopes,  81;  pictures  of,  82, 
83;  occupation  of,  78;  portrait, 
79;  scientific  letters,  8$;  theoreti- 
cal views,  86 
Leibnitz,  208 

Leidy  in  palaeontology,  339 
Lesser's  theology  of  insects,  91 
Leuckart,  136;  portrait,  136 
Leydig,    102;    anatomy   of   insects, 
102;  in  histology,   175;  portrait, 

.175 
Linnaean  system,  reform  of,  130-138 
Linnaeus,  1 18-130;  binomial  nomen- 
clature, 127;  his  especial  service, 


INDEX 


475 


126;  features  of  his  work,  127, 
1 28;  his  idea  of  species,  128,  129; 
influence  on  natural  history,  125; 
personal  appearance,  125;  per- 
sonal history,  119;  portrait,  124; 
helped  by  his  fiancee,  120;  return 
to  Sweden,  123;  and  the  rise  of 
natural  history,  100-130;  the  Sys- 
tema  Naturae,  121,  125,  127;  pro- 
fessor in  Upsala,  123;  celebration 
of  two  hundredth  anniversary  of 
his  birth,  124;  as  university  lec- 
turer, 123;  wide  recognition,  122; 
summary  on,  129-130 

Lister,  Sir  Joseph,  and  antiseptic 
surgery,  302;  portrait,  302 

Loeb,  234;  on  artificial  fertilization, 
441 ;  on  regulation,  440 

Ludwig,  in  physiology,  160;  por- 
trait, 160 

Lyell,  epoch-making  work  in  geol- 
ogy, 332;  letter  on  Darwin  and 
Wallace,   428-430;   portrait,    ^^^ 

Lyonet,  89;  portrait  and  personal- 
ity, 90;  great  monograph  on  in- 
sect anatomy,  91;  illustrations 
from,  92,  93,  94,  95;  extraordi- 
nary quality  of  his  sketches,  92 

M 

Malpighi,  58-67;  activity  in  re- 
search, 62;  anatomy  of  plants,  66; 
anatomy  of  the  silkworm,  63; 
compared  with  Leeuwenhoek  and 
Swammerdam,  87;  work  in  em- 
bryology, 66,  202;  rank  as  embry- 
ologist,  205;  honors  at  home  and 
abroad,  61;  personal  appearance, 
58;  portraits,  59,  204;  sketches 
from  his  embryological  treatises, 
203;  and  the  theory  of  pre-delinea- 
tion,  203 
Man,  antiquity  of,  366;  evolution  of, 

365;  fossil,  342,  366 
Marsh,  O.  C,  portrait,  339 
Meckel,  J.  Fr.,  162;  portrait,  162 
Men,  of  biology,  7,  8;  the  foremost, 

437;  of  science,  7 
Mendel,    315;    alternative    inherit- 
ance, 317;  law  of,  317;  purity  of 
the  germ-cells,  317;  portrait,  316; 
rank  of  Mendel's  discovery,  318, 

319 
Microscope,   Hooke's,   Fig.   of,   55; 
Leeuwenhoek's,  81,  Figs,  of,  82,  83 


Microscopic  observation,  introduc- 
tion of,  54;  of  Hooke,  55;  Grew, 
55;  Ehrenberg,  106;  Malpighi, 
66,  67;  Leeuwenhoek,  81,  84,  85, 
105 
Microscopists,  the  pioneer,  54 
Middle  Ages,  a  remolding  period, 

19;  anatomy  in,  24 
Milne-Edwards,  portrait,  157 
Mimicry,  387 

Mohl,  Von,  268;  portrait,  269 
Miiller,  Fritz,  230;  O.  Fr.,  106 
Miiller,  Johannes,  as  anatomist,  163; 
general  influence,  185;  influence 
on  physiology,  185;  as  a  teacher, 
185;  his  period  in  physiology,  184; 
personality,  185;  portrait,  187; 
physiology  after  Miiller,  188 


N 

Nageli,  portrait,  268 

Naples,  biological  station  at,  454; 
picture  of,  453 

Natural  history,  of  Gesner,  112,  113, 
114;  of  Ray,  115-118;  of  Lin- 
naeus, 1 18-130;  sacred,  no;  rise 
of  scientific,  1 10-130 

Natural  selection,  389;  discovery  of, 
435;  Darwin  and  Wallace  on,  437; 
extension  of,  by  Weismann,  403; 
illustrations  of,  390;  inadequacy 
of,  3Q5 

Nature,  continuity  of,  373;  return 
to,  19;  renewal  of  observation,  19 

Naturphilosophie,  school  of,  160 

Neanderthal  skull,  368 

Needham,  experiments  on  sponta- 
neous generation,  281 

Neo-Lamarckism,  386 

Newport,  on  insect  anatomy,  100 

Nineteenth  century,  summary  of 
discoveries  in,  3 

Nomenclature  of  biology,  126,  127 

Nucleus,  discovery  of,  by  Brown, 
243;  division  of,  256,  314 


Observation,  arrest  of,  17;  renewal 
of,  19;  in  anatomy,  26;  and  ex- 
periment the  method  of  science, 
22,39 

Oken,  on  cells,  241;  portrait,  160 

Omne  viv-um  ex  ovo,  200 

Omnis  cellula  e  cellula,  310 


476 


INDEX 


Organic  evolution,  doctrine  of,  347- 
373;  influence  of,  on  embryology, 
225;  theories  of,  374-414;  rise  of 
evolutionary  thought,  415-441; 
sweep  of  the  doctrine  of,  372 

Orthogenesis,  413 

Osborn,  quoted,  10,  410;  in  pa- 
laeontology, 341 

Owen,  161,  334 


Palaeontology,  Cuvier  founds  verte- 
brate, 327;  of  the  Fayum  district, 
343;  Lamarck  founder  of  inverte- 
brate, 328;  Agassiz,  334;  Cope, 
339;  Huxley,  337;  Lyefl,  332; 
Marsh,  339;  Osborn,  341;  Owen, 
334;  William  Smith,  330;  steps 
in  the  rise  of,  331 

Pander,  germ-layer  theory,  218 

Pangenesis,  Darwin's  theory  of,  307 

Pasteur,  on  fermentation,  294; 
spontaneous  generation,  288;  in- 
oculation for  hydrophobia,  299; 
investigation  of  microbes,  298; 
personality,  296;  portrait,  295; 
his  su[)reme  service,  299;  venera- 
tion of,  294 

Pasteur  Institute,  foundation  of, 
299;  work  of,  300 

Pearson,  Karl,  and  ancestral  inher- 
itance, 321 

Philosophie  Anatomique  of  St.  Hi- 
laire,  424 

Philosophie  Zoologique  of  Lamarck, 
381 

Physiologus,  the  sacred  natural  his- 
tory, 110-112 

Physiology,  of  the  ancients,  179; 
rise  of,  179-194;  period  of  Har- 
vey, 180;  of  Haller,  181;  of  J. 
M  tiller,  184;  great  influence  of 
Muller,  185;  after  MuUer,  188 

Piltdown  Skull,  370 

Pithecanthropus  erectus,  343,  369 

Pliny,  portrait,  16 

Pouchet,  on  spontaneous  generation, 
286 

Pre-delineation,  theory  of,  206;  rise 
of,  Malpighi,  207,  Swammerdam, 
208,  Wolff,  210 

Pre-formation.     See  Pre-delineation 

Primitive  race  of  men,  366 

Protoplasm,  259;  discovery  of,  250, 
262;   doctrine  and  sarcode,    270, 


273;  its  movements,  261;  naming 

of,  269;  its  powers,  260 
Protozoa,  discovery  of,  104;  growth 

of  knowledge  concerning,  104-109 
Purkinje,  portrait,  267 


Rathke,  in  comparative  anatomy, 

163;  in  embryology,  223 
Ray,  John,  115;  portrait,  116;  and 

species,  117 
■Reaumur,  96;  portrait,  98 
Recapitulation  theory,  230 
Recent  tendencies,  in  biology,  445; 

in  embryology,  232 
Redi,   earliest   experiments   on   the 

generation  of  life,   279;  portrait, 

280 
Remak,  in  embryology,  223 
Roesel,  on  insects,  95;  portrait,  97 
Romanes,  413 


Sarcode  and  protoplasm,  273,  275 

Scala  Naturae,  131 

Scale  of  being,  131 

Schaudinn,  Studies  on  Protozoa, 
303;  other  contributions,  304; 
portrait,  304 

Schleiden,  243;  contribution  to  the 
cell-theory,  248;  personality,  247; 
portrait,  246 

Schultze,  Max,  establishes  the  proto- 
plasm doctrine,  272;  in  histology, 
172;  portrait,  273 

Schulze,  Franz,  on  spontaneous  gen- 
eration, 284 

Schwann,  and  the  cell-theory,  242, 
244,  248,  249;  in  histology,  171; 
and  spontaneous  generation,  284 

Science,  of  the  ancients,  return  to, 
112;  conditions  under  which  it 
developed,  8;  biological,  4 

Servetus,  on  circulation  of  the  blood, 

Severinus,  in  comparative  anatomy, 

143;  portrait,  143 
Sexual  selection,  388 
Shells,  evolution  of,  354,  355 
Siebold,  Von,  134,  135;  portrait,  135 
Silkworm,  Malpighi  on,  63;  Pasteur 

on,  299 
Smith,  Wm.,  in  geology,  330 
Spallanzani,  experiments  on  genera- 
tion, 282;  portrait,  283 


INDEX 


477 


Special  creation,  theory  of,  418 

Species,  Ray,  117;  Linnaeus,  129; 
are  they  fixed  in  nature,  352;  or- 
igin of,  352-366  _ 

Spencer,  426;  his  views  on  evolution 
in  1852,  427 

Spontaneous  generation,  belief  in, 
278;  disproved,  292;  first  experi- 
ments on,  278;  new  form  of  the 
question,  281;  Redi,  279;  Pas- 
teur, 288;  Pouchet,  286;  Spallan- 
zani,  282;  Tyndall,  290 

Steno,  on  fossils,  322 

Straus-Diirckheim,  his  monograph, 
96;  illustrations  from,  loi 

Suarez,  and  the  theory  of  special 
creation,  410 

Swammerdam,  his  Biblia  Naturae, 
73;  illustrations  from,  74,  76; 
early  interest  in  natural  history, 
68;  life  and  works,  67-77;  love 
of  minute  anatomy,  70;  method  of 
work,  71;  personality,  67;  por- 
trait, 69;  compared  with  Mal- 
pighi  and  Leeuwenhoek,  87 

System,  Linnaean,  reform  of,  130- 
138 

Systema  Naturae,  of  Linnaeus,  121, 
127 

T 

Theory,  the  cell-,  242;  the  proto- 
plasm, 272;  of  organic  evolution, 
345-368;  of  special  creation,  410 

Tyndall,  on  spontaneous  generation, 
289;  his  apparatus  for  getting  op- 
tically pure  air,  290 

Type-theory,  of  Cuvier,  132 


Uniformatism,    and    catastrophism, 

333 

V 
Variation,  of  animals,  in  a  state  of 

nature,  388;  origin  of,  according 

to  Weismann,  402 
Vesalius,  and  the  overthrow  of  au- 


thority, in  science,  22-38;  great 
book  of,  30;  as  court  physician, 
35;  death,  36;  force  and  inde- 
pendence, 27;  method  of  teaching 
anatomy,  28,  29;  opposition  to, 
34;  personality,  22,  27,  30;  phys- 
iognomy, 30;  portrait,  29;  prede- 
cessors of,  26;  especial  service 
of,  37;  sketches  from  his  works, 

31,  33,  34,49 
Vicq  d'Azyr,  146;  portrait,  147 
Vinci,  Leonardo  da,  and  fossils,  322 
Virchow,  and  germinal  continuity, 

225;  in  histology,  174;    portrait, 

174 
Vries,  Hugo  de,  his  mutation  theory, 
408;   portrait,   409;   summary  of 
theory,  412 

W 

Wallace,  and  Darwin,  428;  his  ac- 
count of  the  conditions  under 
which  his  theory  originated,  435; 
portrait,  436;  writings,  435 

Weismann,  the  man,  405;  quotation 
from  autobiography,  407;  per- 
sonal qualities,  405;  portrait,  406; 
his  theory  of  the  germ-plasm,  398- 
405;  summary  of  his  theory,  411 

Whitney  collection  of  fossil  horses, 

357 

Willoughby,  his  connection  with 
Ray,  115 

Wolff,  on  cells,  240;  his  best  work, 
211;  and  epigenesis,  205;  and 
Haller,  211,  214;  opposed  by 
Bonnet  and  Haller,  211;  his  pe- 
riod in  embryology,  205-214;  per- 
sonality, 214;  plate  from  his 
Theory  of  Generation,  209;  the 
Theoria  Generationis,  210 

Wyman,  Jeffries,  on  spontaneous 
generation,  289 


Zittel,   in  palaeontology,   340;   por:- 
trait,  341 


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